The White House has sent the General Accounting Office a detailed report showing that former deputy chief of staff Michael K. Deaver played a key role in White House discussions on acid rain before leaving the government to become a lobbyist for Canada on acid rain and other issues, according to administration sources.

The report, in a "fact-finding" letter from presidential counsel Peter J. Wallison, is based on interviews with other White House and administration aides who participated in the discussions last spring of acid rain and on an examination of documents from their files.

Officials said the report draws no conclusions about whether Deaver violated conflict-of-interest or lobbying rules, but documents his role in White House deliberations.

The officials said Deaver's role was described by some participants as seeking to change President Reagan's policy on acid rain and by others as a concern for the public relations aspects of Reagan's March 1985 summit with Canadian Prime Minister Brian Mulroney.

The Canadian government had been pressing the administration to take a more aggressive stance toward cleaning up acid rain, a form of pollution that many scientists say is harming lakes, forests and wildlife in Canada and the northeastern United States.

Deaver has previously acknowledged taking part in the White House discussions on acid rain, but maintained it was in line with his regular duties.

"I was doing my job in the White House," he said in a telephone interview last week.

Deaver is one of several former officials allowed to keep his White House pass, and he retains a close personal relationship with the president and First Lady Nancy Reagan. At the White House, he was concerned primarily with the image-making and communications aspects of Reagan's presidency.

Often credited by others with aiding Reagan's successful efforts to shift public opinion, Deaver was not widely regarded as a policy expert. Some officials involved in the acid rain issue said they were surprised when Deaver expressed an interest in it.

Deaver said on television recently that he is not knowledgeable about the complexities of the issue.

He has denied any wrongdoing in the matter, which is being investigated by the General Accounting Office at the request of Rep. John D. Dingell (D-Mich.), chairman of the House Energy and Commerce Committee. The Office of Government Ethics also is reviewing it.

The White House discussions on acid rain led to the appointment by the United States and Canada of special representatives on the problem at the Reagan-Mulroney summit. Officials have said that Deaver and former assistant secretary of state Richard Burt were the prime movers behind Reagan's decision to appoint the representatives, a move that resulted in a shift in the president's position.

In January, the special envoys presented a report calling for a major new effort to address acid rain, as Canada has been seeking for some time. Reagan, who previously had resisted such proposals, endorsed the report when Mulroney was visiting here last month.

The two special envoys were former U.S. transportation secretary Drew L. Lewis and former Ontario premier William G. Davis.

Last May, after the special envoys had been named, Deaver left the White House and opened a lobbying and communications firm, Michael K. Deaver & Associates, and was retained by Canada to advise them on acid rain and other issues for $105,000 a year.

Deaver said last week that after leaving the White House he discussed acid rain with Lewis. He said the discussion was "not on the substance" of the report, but rather the timing of its release. Deaver said he has not discussed the issue with other administration officials.

Federal law prohibits former government employes from lobbying on any matters in which they "participated personally and substantially."

The law also prohibits lobbying the agencies where officials previously worked for a year after leaving office. Another provision bars former officials from lobbying the government for two years on matters that were under their responsibility in their final year in office.

As part of its investigation, the General Accounting Office asked the White House to provide details about Deaver's involvement in the discussions on acid rain. The GAO also interviewed Lewis, sources said. It is not known when the agency's report will be completed.

White House officials said the Wallison report was "not an investigation" but a "fact-finding" letter to the GAO. The report was started under Wallison's predecessor, Fred Fielding. Fielding, who recently left the White House, has said he recused himself from the Deaver matter when an official of Deaver's firm asked Fielding whether he would be interested in joining the firm.

Deaver said he has not seen the Wallison letter. He said he has "reassembled" his recollection of the discussions on acid rain and retained the Washington law firm of Arnold & Porter. Deaver said he is "confident" the GAO probe will support his contention that his role in the acid rain issue was strictly part of his White House duties.

Since leaving the White House, Deaver has become a highly visible lobbyist for several countries and corporations seeking to influence administration policy, including Canada, Mexico, South Korea and Saudi Arabia. Some White House officials said they were concerned when Deaver met recently with Office of Management and Budget Director James C. Miller III to discuss efforts by his client, Rockwell International, to persuade the administration to buy more B1 bombers. Deaver said the meeting was proper because the budget office was not part of his former White House office.

Less than a year after leaving the White House, Deaver has been negotiating to sell his firm to the British advertising and communications giant Saatchi and Saatchi for$18 million, although the London firm recently has expressed misgivings about the negative publicity surrounding Deaver's activities.