In a newly discovered White House computer note, former national security adviser Robert C. McFarlane discussed the purging of National Security Council files around the time the Iran-contra affair erupted last year, Rep. Lee H. Hamilton (D-Ind.) said yesterday.

Hamilton, the chairman of the House Iran-contra panel, said the note confirms previous evidence that "McFarlane was engaged in efforts to keep the story from coming out."

"It is direct evidence and will be released," Hamilton said, without specifying when.

The previously undisclosed McFarlane note is one of about 80 computer messages that were found as a result of a new search of the NSC computer system done at the request of the select House and Senate Iran-contra committees.

Three of the other recently discovered messages were released last week, including a February 1986 message from then-national security adviser John M. Poindexter that said Vice President Bush was "solid" in support of the secret sale of arms to Iran to gain release of U.S. hostages. The note on Bush has rekindled interest in the unresolved question of the vice president's role in the Iran arms sales.

Reps. Peter W. Rodino Jr. (D-N.J.) and Dante B. Fascell (D-Fla.), who are members of the House panel, said the recent discovery of the computer messages demonstrates that there is still relevant information that has not yet been made public on the worst crisis of the Reagan presidency.

House Democratic aides said that the new search of NSC internal computer messages involved extensive negotiations with the White House and was not done until last month, which was after the release of the final report of the House and Senate select committees.

Rodino and Fascell, who in the report criticized the administration for withholding information, urged the White House now to release promptly all the previously undiscovered computer notes as well as thousands of pages of sworn testimony and other documents obtained by the House and Senate panels.

"The committee voted to release all the depositions," Fascell said in an interview. "It would be useful if the White House hurries up and finishes their review. I don't think it is satisfactory to say, 'well, the report is out.' That doesn't mean our work is finished."

The circumstances surrounding last week's release of some of the computer notes has reopened tensions among some lawmakers and staff members on the House and Senate Iran-contra panels.

From the outset of the investigation, staff and members on the House committee took a more confrontational approach to the White House and senior administration officials than did the Senate members and aides.

However, Hamilton as chairman of the House panel consistently avoided confrontation. Some aides on the House committee faulted him for what they described as his diplomatic -- almost professorial -- demeanor.

In a telephone interview yesterday, Hamilton said his nonconfrontational approach proved effective. "Information did not always come to us as quickly as we would have liked to have had it," he said, "but in the end we got it."

A glimpse of the behind-the-scenes disagreement between some House and Senate members was reflected in the different views on White House cooperation filed in the supplementary section of the final report.

The chairman and vice chairman of the Senate committee, Daniel K. Inouye (D-Hawaii) and Warren B. Rudman (R-N.H.), in their supplement, praised the White House for rising "above partisan considerations" in cooperating with the committees.

Inouye and Rudman also appeared to embrace the White House's view that a new computer search was futile and said "nobody has any reasonable expectation that the {new} computer 'dump' will produce any new information . . . . "

In a separate supplement, Fascell, Rodino and five other Democratic members of the House panel said lack of White House cooperation hurt the probe. "Delayed production {of documents}, nonproduction and noncompliance with committee requests made witness interviews difficult, made it necessary that some witnesses be reinterviewed, and complicated the committees' preparation for public hearings," said the seven Democrats.

They specifically cited the White House's handling of the request for the new computer search.

Patrick J. Carome, a House committee lawyer involved in the computer negotiations, said there were numerous meetings with White House aides and "a number of hurdles had to be cleared with the White House that ground up a lot of time."

Carome said the House committee's effort to develop a computer program for the search was hurt when the White House, citing national security concerns, refused to allow House computer experts access to the NSC computer system.

Carome said White House officials kept saying the effort was a "waste of time."

But, Carome said, the 80 or so recently discovered computer messages are all new and would never have been found if the House committee had not pushed for the new search. (The new search produced a total of 96 documents, but about 15 of them were duplicates.)

Despite their initial reluctance to press for the new computer search, Inouye and Rudman issued the new memo on Bush and two others last week in a press release that did not mention the House committee, a decision that angered some House aides.

Hamilton said yesterday that Inouye informed him of the release about the time it was issued and he did not object to it. "I appreciated being advised it was being released," Hamilton said. "Most {press releases} done throughout the hearings were done in all of our names. I don't know why in this instance they chose to release it in their names alone."

House aides familiar with the new search as well as members who pushed for it said they did not see the notes before they were released.

"I don't have the slightest idea what was recovered," said Fascell, who was among those who pressed for the new search. "I don't know what was used as a basis for making a judgment on what should be released and what should not be released.

"The Senate did whatever it wanted anyway {throughout the probe} as far as I can tell," Fascell added.