A national accounting firm and as many as 15 former directors of Maryland's defunct S&L watchdog agency are among the potential targets of civil lawsuits recommended by the special counsel who investigated the state's savings and loan crisis, sources familiar with the report said yesterday.

Wilbur D. Preston Jr., who concluded his 10-month study on Friday, also recommended that Gov. Harry Hughes authorize civil suits against a second accounting company and an appraisal firm that performed work for the defunct Old Court Savings & Loan Association of Baltimore, where depositor runs a year ago triggered the thrift industry crisis.

The new details of Preston's final recommendations to the governor emerged a day after the special counsel delivered a six-page letter to Hughes summarizing his findings since January, when he turned over an exhaustive 457-page report on the origins of the financial debacle that paralyzed large segments of the $9 billion industry beginning last May.

In all, Preston recommended six new civil suits. The state already has brought three multimillion-dollar suits against the former owners of Old Court, Community and First Maryland savings and loans.

All but one of the six suggested lawsuits are directed at individuals or firms associated with either Old Court or Merritt Commercial Savings & Loan of Baltimore.

The sixth would be brought against former directors of the Maryland Savings-Share Insurance Corp., the private corporation financed by the savings and loan firms themselves to police their operations and pay off depositors should a thrift fail. MSSIC's lax oversight of the industry was severely criticized in Preston's original report.

One source said that a dozen to 15 former MSSIC directors could be the likely targets of such a suit.

Preston, according to the sources, also has recommended that the state seek to recover money from Old Court's accounting firm, Glass and Associates, and a Baltimore appraisal firm, Amernick and Associates. The appraisal firm, said the sources, was responsible for placing an inflated value on a parcel of land in Prince George's County that served as the collateral for the purchase of Old Court by Jeffrey Levitt and Allan Pearlstein in 1982. Preston's original report said the $5.5 million appraisal on the 250-acre parcel was approximately nine times its selling price.

The special counsel has also urged Hughes to bring suit against Alexander Grant and Co., a national accounting firm based in Chicago. Alexander Grant served as the accounting and auditing firm for Merritt, which was placed under conservatorship last year before being acquired by Chase Manhattan Corp.

It was reported earlier that Preston has recommended suits against Merritt's former owner, Gerald Klein, and the Baltimore law firm of Venable, Baetjer and Howard, which jointly represented Old Court and MSSIC. The sources said yesterday that the suggested suit against Klein also would seek to recover money from Robert Gibbs, who sold his share of Merritt to Klein in November 1984.

Asked to estimate the potential amount of money that could be recovered from the six possible suits, one source familiar with Preston's investigation said, "I don't think anybody really has a good fix on it, but I think you are talking tens of millions of dollars in potential recoveries."