For more than a year, the U.S. Postal Service has had before it a recommendation that the two largest organizations for the elderly be denied their nonprofit mailing status because of their ties to a large Philadelphia insurance company.

The 11-million-member American Association of Retired Persons and its 500,000-member affiliate, the National Retired Teachers Association, are "just a marketing agent" for Colonial Penn Group, the insurance company, according to Arthur S. c/ahn, former assistant general counsel of the Postal Service, who headed a 2 1/2-year investigation.

Lloyd Wright, a spokesman for the two groups of the elderly, rejected Cahn's charge as "wholly unfounded," adding that the associations are "involved primarily in educational service programs."

The Postal Service investigation is one of a number of developments that cast more light on the relationship between Colonial Penn and the AARP and NRTA.

The AARP's former national treasurer testified in a recent trial in Los Angeles that his efforts to learn about the organization's financial affairs, including fees charged by its lawyers, had produced "nothing." Similarly, a former executive director testified that she couldn't learn who the members were.

Recently obtained minutes of a closed meeting of the AARP-NRTA joint executive committee two years ago in Kissimmee, Fla., reveal that the groups' "honorary president," Leonard Davis, 76, of Palm Beach, Fla., the principal stockholder of Colonial Penn, was apparently granted sweeping powers over the organizations. Davis annually receives about $3 million in dividends from Colonial Penn Group, which gets the bulk of its business from the associations.

In Morgantown, W. Va., AARP former president Alice VanLandingham, in a letter to 150 other unpaid AARP volunteer leaders, charged that the AARP, without her knowledge, had imprinted her signature on its solicitations to members encouraging them to buy CPG insurance. The association denied her charge.

Guides issued by AARP-NRTA headquarters to 2,700 local chapters explain how to prevent competition with CPG offerings of health, life, auto and homeowner insurance, and travel and employment services.

In Madison, Wis., where an otherwise strict health-insurance law exempts CPG coverage sold to AARP members, the state insurance commissioner was admonished by AARP-NRTA headquarters when he requested the help of local chapters in advising the elderly on the prudent purchase of coverage to supplement Medicare.

In Boston, a Massachusetts assistant attorney general confirmed that he is conducting an investigation relating "to potential unfair and deceptive trade practices" in the sale of CPG insurance -- the only kind promoted by the two associations.

Former Postal Service lawyer Cahn, now an official of a federal agency in Sacramento, told a reporter that even as of a year ago, the evidence in hand was "more than enough" to show that the associations are a marketing agent for Colonial Penn and sufficient to show that they "are not educational or charitable, in that their primary purpose is to market Colonial Penn insurance."

On a single piece of third-class mail, a nonprofit permit saves an organization about 8 cents.

Nonprofit status and low annual membership fees helped AARP, in most of the 1970s, to enlist new members at a rate or more than 3,000 a day. One of four Americans 55 and older now belong.

Usually, two or three or each 10 new members buy insurance from CPG, which in 1977 alone mailed out 192 million "solicitation kits."

The low membership fees are made possible by "administrative allowances," currently about $13 million a year, paid to AARP and NRTA by Colonial Penn Group in exchange for exclusive access to association membership lists and publications.

The Postal Service hasn't acted on Cahn's recommendation. The service says it is studying the recommendation, although it expressed hope in September for a decision "in the next months or so."

Under different laws, the associations are exempt from income tax. The district director of the Internal Revenue Service in Baltimore had proposed to revoke the AARP-NRTA exemptions. Apparently without investigation, the IRS, in an unsigned "national office technical advice memorandum," last March, concluded that the associations have shown "that they are not controlled by" CPG.

In the Los Angeles trial, AARP former national treasurer and New Hampshire state Rep. Francis Seely and former executive director Harriet E. Miller appeared as wtnesses in Superior Court for AARP member Anne M. Costello.

She was treated for 98 days, 59 of them in intensive care, in a hospital accredited to provide acute as well as rehabilitative care. But a CPG subsidiary refused to pay her $21,000 bill on the ground that her "in hospital" policy didn't cover her treatment.

After lawyer William M. Shernoff sued CPG and AARP, which had promoted the policy, for making allegedly fraudulent claims and allegedly breaching a duty of good faith, the company paid $3,000.

Costello seeks compensatory and unspecified punitive damages. The trial began Dec. 19.

Seely testified that until he complained, even AARP-NRTA board members didn't have access to copies of the insurance contract under which CPG makes payments through a conduit trust to a second conduit, the NRTA-AARP Administrative Trust Fund.

Similarly, Harriet Miller testified that while exective director she hadn't seen "any of the basic documents" for the trusts, which were drawn by the late Philip L. Handsman, a CPG stockholder, first AARP general counsel, and friend of Leonard Davis.

Decisions about the insurance the associations promoted were made not by their directors, who had "nothing to say," but by a CPG subsidiary, National Association Plans Inc., Seely testified. He and Miller agreed that there was no independent evaluation and no review of what rival insurers might offer.

Association members accounted for most of CPG's 1977 revenues of $566.9 million, up 27 percent over 1976, and for after-tax income of $59.8 million, up 20 percent. In the five-year period ended Dec. 31, 1975, according to a Forbes magazine survey, CPG's 33.5 percent average return on equity and total capital was the highest among the 929 corporations with sales of at least $250 million.

Leonard Davis, who realized $80 million from sales of CPG stock in an eight-year period ended in 1976, still owns 17.6 percent and controls 1.6 percent, for a total of 3,093,530 shares. Their market value at the close of trading yesterday was $76.2 million.

The minutes of the closed meeting in Kissimmee at what Davis got sweeping powers over the associations' affairs were a major factor in the decision of former Postal Service attorney Cahn to recommend revocation of the association's eligibility for the nonprofit permits they use for their own materials and for solicitations for CPG insurance.

The minutes were not among the thousands of pages of documents offered by the associations to postal investigators, although the minutes of a meeting not attended by Davis -- because he was undergoing surgery -- were. AARP-NRTA supplied "all of the information they have requested," said spokesman Wright.

The joint executive committee convened the closed session on Jan. 30, 1977, after excluding Miller. In Los Angeles, she testified that she never saw the minutes, until "months after," when she was asked to, and did, sign them.

The minutes say she was "advised" that the committee unanimously had passed a resolution requesting Davis, "on a regular basis," to provide "the benefit of his financial, accounting and management expertise for the consideration of the committee in formulating decisions and also to provide legal, accounting and other liaison on a continuing basis."

Davis and "such associates [as] he selects" will be enabled to meet with AARP-NRTA staff, which "shall cooperate to the maximum extent," the committee directed. The minutes noted "a consensus to have Leonard Davis' advisory assistance recognized with appreciation."

Davis attended the closed session, along with: Ruth O. Lana, the other honorary president and an old associate; four key AARP-NRTA directors; Lahr; three partners in Miller, Singer, Michaelson, Brickfield & Raives, a New York law firm with offices in the same building as CPG, its main client, and five past, present and future AARP-NRTA presidents, including Alice VanLandingham

VanLandingham, in a letter to the other unpaid voluntary leaders, wrote that after 12 years of service to AARP and its "great purpose" of helping the elderly, she had to protest its domination by Davis and what she called the "controlling group." It consists mainly of special counsel Lahr and law partners Alfred Miller, Lloyd I. Singer and Cyrus F. Brickfield, she said in a phone interview.

Davis "does everything" through the attorneys, she said. Similar claims were made in Los Angeles and in a sworn affidavit by former treasurer Seely, who charged that without telling AARP directors, Lahr initiated such major actions as a legal challenge to the Postal Service for denying nonprofit status to AARP-NRTA pharmacies.

Brickfield has denied VanLandingham's charges. In a letter, to AARP volunteer leaders, Brickfield wrote that the "controlling group" is nothing more than "a number of individuals who... have contributed their expertise... and significantly assisted our association's achievements..."

Brickfield became his law firm's Washington partner in 1975, with an office adjoining AARP's executive director's. He hald that post form 1967 to 1970, when he became AARP-NRTA's legislative counsel, and now has succeeded Harriet Miller as executive director.

Lloyd Singer, his partner, is a former CPG chariman and chief executive officer, and a former president of its Colonial Penn Life Insurance and CPG Data subsidiaries.

For Van Landingham, the last straw was the firing of Harriet Miller, which, both women contend, Davis engineered. Miller's lawsuit, filed in D.C. Superior Court, has been merged with a countersuit in which AARP charges that she violated a settlment agreement under which she would be a consultant, for two years, at her old annual salary of $60,000 -- $20,000 less than the salary of executive director Brickfield.

In addition to Davis and CPG, Miller's suit names as defendants Brickfield and his partners and the associations. She charges that the associations are a "convenient and effective cover" for a "vast profit-making empire." That's false, Brickfield has said.

The AARP-NRTA headquarters documents on how chapters should deal with potential competition to CPG insurance include a warning that making value comparisons is "extremely difficult." Members should be reminded "never to accept a comparison only of cost and benefits," says a chapter guidebook obtained by The Washington Post.

In 1974, buyers of CPG health insurance got back 61.9 cents for each premium $1. Buyers of some rival policies averaged 90.6 cents.

The guidebook says that if an insurance salesman approaches a chapter, "it should be remembered that sponsorship or recommendation is prohibited by the chapter's constitution and bylaws."

The "AARP Chapter Handbook" says that the purpose of each chapter's insurance committee is "to provide information about the AARP Group Halth Insurance Plans and the AARP recommended insurance policies." To keep members' names away from CPG rivals, the handbook terms it "essential" for each chapter to adopt "safeguards... to protect all membership lists and records from release or distribution."

Chapter bylaws, raising a further barrier to competition, say that a chapter can't offer its members "any commodities or services already offered by the associations.

In Wisconsin, for complex legal reasons, AARP-NRTA plans escape regulation that applies to CPG's rivals.

Hoping to have the associations assume the "public trust" responsibilities that the state can't exercise, Insurance Commissioner Harold R. Wilde asked the Wisconsin AARP-NRTA chapters to cooperate.

Because he can't require the chapters or CPG to distribute to senior citizens a state official guide to Medicare supplementary insurance that other companies must provide, Wilde asked the chapters to find out, for example, if they tell members that AARP-NRTA plans aren't regulated, tell them how the plans meld with Medicare, and warn them against "stacking" various types of coverage.

The response came not from Wisconsin, but from Washington, where an AARP-NRTA membership official, in a letter to Wilde, claimed, "Our associations, of course, vigorously support full disclosure of all relevant information..."

Wilde replied that the letter sounded "as if it were some sort of cannon shot across the bow." He told the official, James F. Sullivan: "If your organizations truly support [better] disclosure, I would suggest that you get in touch with your insurance carrier [CPG], with whom we have had inconclusive discussions... and have it develop new outlines of coverage and new advertisements for your various plans."