The so-called Keating Five senators applied pressure on regulators in support of "probably the worst institution in America," Charles H. Keating Jr.'s Lincoln Savings and Loan, a federal regulator said Wednesday.

William K. Black said one result of the senators' pressure was to delay enforcement actions against Lincoln - ultimately leading to greater losses for taxpayers.Black was testifying before the Senate Ethics Committee's public hearings of the case of the senators, who are accused of improperly intervening with federal regulators on behalf of the Arizona financier.

Black described as improper a request that one of the senators, Dennis DeConcini, D-Ariz., made in a disputed April 9, 1987, meeting the senators held with regulators.

DeConcini asked the regulators to waive a rule that would limit Lincoln's ability to make direct investments and would have the effect of exposing the thrift to direct regulatory control.

Black, a senior deputy counsel with the Federal Home Loan Bank Board, generally supported the earlier testimony of two other regulators that DeConcini, an Arizona Democrat, sought to have the regulators waive a rule limiting Lincoln's ability to make risky direct investments, and that he used the word "we," suggesting he was speaking for all the senators.

Black also went beyond previous testimony to say he believed political pressure from the senators led to later actions by the bank board that allowed Lincoln to significantly expand junk bonds and direct investments.