The Office of the U.S. Trade Representative is looking into allegations that one of its former senior officials, now a lobbyist for Michael K. Deaver, contacted her former colleagues on behalf of Deaver's foreign clients, a spokesman said yesterday.

Doral S. Cooper, who resigned her $72,300-a-year post last August as assistant U.S. trade representative for Asia, Africa and the Pacific, is covered by the federal law that prohibits senior officials from lobbying their former agencies for one year, ethics officials said.

But Pamela G. Bailey, a spokesman for Michael K. Deaver & Associates, said a report in The Washington Times that Cooper had repeatedly lobbied her former agency was "absolutely false . . . . Doral Cooper had no contacts of a substantive nature with the U.S. Trade Representative's office that were reportable under the Foreign Agents Registration Act or were prohibited under the Ethics in Government Act."

Deaver, who resigned last May as White House deputy chief of staff to form a multimillion-dollar consulting firm, is already under investigation because of allegations that he may have violated federal conflict-of-interest laws in lobbying executive branch officials. The Justice Department is considering Deaver's request that an independent counsel be named to investigate the allegations, which Deaver, a longtime friend of President Reagan, says are groundless.

Roger Bolton, spokesman for the U.S. Trade Representative's office, said the office has begun an inquiry into whether Cooper lobbied trade officials in violation of federal ethics laws. Cooper, like other members of Deaver's firm, is registered as a foreign agent.

Deaver has met twice with Clayton Yuetter, the U.S. trade representative, on behalf of foreign clients, according to Bolton, who said there was nothing unusual about such meetings. He said Deaver spoke to Yuetter about South Korea's desire to resolve two cases brought by the office that accuse the country of unfair trading practices.

Bolton said the office's lawyers ruled that the meetings with Deaver did not violate ethics rules because the Cabinet-level agency, which is under the Executive Office of the President, is not considered part of the White House. Bailey said a similar finding that the president's Office of Management and Budget is not part of the White House made it proper for Deaver to meet with OMB Director James C. Miller III on behalf of Rockwell International.

Another Deaver lobbyist, Lisa Barry, who resigned Jan. 1 as special assistant to the deputy U.S. trade representative and joined Deaver six days later, repeatedly contacted trade officials on behalf of foreign clients, according to trade officials. But Bailey and ethics officials said Barry is not covered by the one-year ban on lobbying her former agency because she was not sufficiently senior in rank.

Bill Merkin, the deputy assistant trade representative responsible for Canada, said he frequently discusses U.S.-Canadian trade relations with Barry and that she bought him breakfast at the Hay-Adams Hotel in January. He said he understood Barry was not covered by the lobbying ban. Bolton said Barry is prohibited only from discussing a specific matter she handled while at the trade representative's office.

Deaver's filings with the Justice Department show contacts with other Cabinet officials which, while not illegal, portray a firm with a high degree of top-level access:

*In January, Deaver's firm twice contacted Commerce Secretary Malcolm Baldrige on behalf of South Korea regarding a department case that accused that country of unfairly "dumping" photo albums on the U.S. market. Deaver's firm has had $725,000 in contracts with South Korean interests, some of which have been terminated.

*In February, Deaver's firm twice contacted Treasury Secretary James A. Baker III -- who was Deaver's immediate superior when Baker was White House chief of staff -- on behalf of Panama-based CBI Sugar Group, which is concerned about U.S. sugar import quotas. The firm also contacted Secretary of State George P. Shultz on the sugar issue in February. CBI Sugar has paid Deaver's firm $300,000.

*In October, the firm contacted Deputy Treasury Secretary Richard G. Darman, who was Baker's deputy at the White House, on Canada's behalf. Canada has a $105,000-a-year contract with Deaver's firm.

Deaver's firm also contacted leading Treasury Department enforcement officials 28 times in four months in an effort to help South Korean's Daewoo Corp. settle a $25 million customs fraud case.