The accounting firm of Coopers & Lybrand, charged by federal regulators with making a faulty audit of a failed Colorado savings and loan, has agreed to tighten its auditing procedures, the government said yesterday.

The Office of Thrift Supervision (OTS), the agency responsible for the cleanup of failed thrifts, said its settlement with Coopers & Lybrand was its first major enforcement action against a big accounting firm. Experts have said accountants played an important role in the $500 billion savings and loan scandal, but until now regulators have focused their attention mainly on S&L operators and directors.

The charges against Manhattan-based Coopers & Lybrand stemmed from its 1986 audit of Silverado Banking, Savings and Loan Association of Denver, whose board of directors included President Bush's son Neil. The collapse of Silverado in December 1988 is expected to cost taxpayers $1 billion.

The OTS had leveled charges against both Coopers & Lybrand and Arthur L. Knight, who headed the firm's team that conducted the Silverado audit.

The auditors "did not possess the expertise required to properly complete the Silverado audit," the office said in a legal brief released with its announcement.

This case "says loud and clear that we hold accountants, lawyers and other professionals accountable for their actions, just as we do S&L directors and officers," said Timothy F. Ryan, director of the OTS, in a written statement.

In its settlement, the accounting firm agreed to meet a number of auditing requirements over the next five years.

In addition, Knight agreed not to audit any insured savings institutions.