A senior thrift regulator told the Senate Select Committee on Ethics yesterday that he believes intervention by five senators on behalf of Charles H. Keating Jr.'s Lincoln Savings and Loan Association delayed enforcement action against the failing thrift "at greatly increased loss" to U.S. taxpayers.

But William K. Black, former general counsel of the Federal Home Loan Bank Board in San Francisco, offered corroboration only in the case of Sen. Alan Cranston (D-Calif.), drawing angry protests from lawyers for most of the senators, who contended that the allegation was unfair and unsubstantiated.

At the end of yesterday's proceedings, Committee Chairman Howell Heflin (D-Ala.) announced that the panel plans to order testimony from James Grogan, chief lobbyist for Keating, under a grant of limited immunity that would not preclude criminal prosecutions of anyone, including Grogan.

Sen. Warren B. Rudman (R-N.H.), committee vice chairman, said Grogan will probably testify next Wednesday or Thursday, first in closed-door session and then in public hearings that are expected to conclude shortly thereafter.

Heflin said the committee "has not and will not consider" seeking an immunity order for Keating, who is facing trial in California on state fraud charges and under investigation by federal authorities. Rudman said Grogan, as Lincoln's lobbyist, had "more contact and more knowledge" about the case than Keating anyway.

Although other regulators have challenged the propriety of the senators' intervention, Black in his testimony yesterday was the first to assert that it had any effect on government action in regard to Lincoln.

Black pointed to a May 20, 1988, decision by the bank board that allowed Lincoln to expand its junk bonds and high-profit, high-risk investments and noted that a Cranston aide called FHLBB officials two weeks earlier to say Cranston was "very concerned" about an earlier proposal for stiffer regulation of Lincoln.

"This led to greatly increased losses for the {federal thrift} insurance fund initially, and the taxpayers eventually," said Black, who was one of four regulators summoned to meet with the senators on Lincoln's problems in 1987.

Lincoln, in Irvine, Calif., was seized by the government in April 1989, at an estimated cost of more than $2 billion to taxpayers.

In his daylong appearance, Black generally supported earlier testimony by two other former regulators, including Edwin J. Gray, former chairman of the bank board, that Sen. Dennis DeConcini (D-Ariz.) made an improper proposal at two April 198, meetings with regulators to ease restrictions on Lincoln. He also agreed with colleagues that DeConcini repeatedly used the word "we" without contradiction from the other senators in attendance. The five lawmakers -- Sens. John Glenn (D-Ohio), John McCain (R-Ariz.), Donald W. Riegle (D-Mich.), Cranston and DeConcini -- are under investigation by the ethics panel for various degrees of intervention on behalf of Keating, who gave $1.3 million to their campaigns and causes.

Asked if he found anything improper at a meeting he attended April 9 with the senators, Black said he did. "This is an institution," he said, referring to Lincoln, "that is probably the worst institution in America and, instead of people trying to help bring it under control, five U.S. senators were pushing us in the opposite direction . . .startingly the wrong direction."

After the April 9 meeting, when the regulators said they were referring the Lincoln case to the Justice Department for criminal investigation, McCain, Glenn and Riegle ended their intervention on behalf of Lincoln, according to evidence in the case. But evidence shows that Cranston and DeConcini persisted in their efforts until shortly before Lincoln was seized by the government a year later.

Infuriated by Black's failure to distinguish among the senators in light of their varying roles, John Dowd, McCain's attorney, took Black through a lengthy cross-examination culminating in an acknowledgement by Black that McCain did nothing to influence government action in his opinion.

Earlier, attorneys for Cranston and DeConcini objected to committee counsel Robert S. Bennett's questioning that led to Black's testimony about the impact of the senators' actions, which James Hamilton, DeConcini's lawyer, referred to as "reckless and irresponsible."

Black's mention of Cranston was prompted by questions from Bennett and referred to a phone call to top FHLBB officials by Carolyn Jordan, the senator's banking aide. The call came on May 6, 1988, the day after the board proposed enforcement action against Lincoln that the company's officials opposed and 14 days before it adopted modified rules more to Lincoln's liking.

According to a memorandum from Jordan to Cranston, she told regulators that the senator was "very concerned" about the proposal.

Under questioning from Bennett, Black acknowledged that Keating viewed him as a "problem regulator." A memo that has been introduced in evidence, written by Keating to Grogan in July 1987, is titled, "Highest Priority -- Get Black." It reads in entirety: "Good grief -- if you can't get Wright {apparently then-House Speaker Jim Wright of Texas} and Congress to get Black -- kill him dead -- you ought to retire."

Wright, who had been introduced to Keating by Glenn and had controversial ties with Texas thrift institutions, later resigned amid a House ethics committee inquiry into his conduct.