The White House changed administration signals again on El Salvador yesterday, disowning an earlier suggestion that the press was exaggerating the importance of the story.

Last week a high State Department official held a background briefing to complain that the press was overemphasizing U.S. involvement in El Salvador at the expense of other important foreign policy issues.

His remarks were partially rebuffed the next day by his boss, Secretary of State Alexander M. Haig Jr., who also identified the official as John A. Bushnell, the acting assistant secretary of state for inter-American affairs. Yesterday, the White House disassociated itself entirely from Bushnell's complaint, saying he was not speaking for the president.

"I think he was speaking for himself," White House press secretary James S. Brady said.

Brady and other White House officials insisted that Bushnell had acted on his own, although it is no secret that there are those in the White House who believe that El Salvador is diverting public attention from the president's economic program.

"Our impression is that this [El Salvador] story is running about five times as big as it really is," Bushnell said in his background briefing Thursday under ground rules that prohibited reporters from naming him as the source.

In a reference to the 54 American advisers that have been sent to El Salvador, the State Department official declared: "Judging by the press coverage of this, I would have thought we had deployed a whole division."

The lecture seemed a curious one to many attending the briefing. The El Salvador issue had been so prominently raised by Reagan and by Haig as part of a campaign to make the sending of outside arms to Salvadoran rebels a test of the administration's resolve in the hemisphere.

On the MacNeill-Lehrer Report the following day, Haig was asked why El Salvador isn't "a big deal" anymore.

"I wouldn't suggest that it's not that big a deal," Haig replied. Later in the program he identified Bushnell as the official who had done the background briefing.

Bushnell is a career official who had been considered to be in line for an ambassadorship.

Yesterday, the president won his first test of congressional support for the stepped-up involvement in El Salvador when a Senate appropriations subcommittee approved his plan to aid that Central American ally with $5 million in military sales credits. Six Republican senators supported the measure; Sen. Mark Hatfield (R-Ore.) and Sen. Patrick Leahy (D-Vt.) were the only dissenters. Sen. Daniel Inouye (D-Hawaii) abstained.

At his daily White House briefing, Brady said that the president still thinks the Salvadoran issue is very important. The press secretary also said the president does not subscribe to the view that the story has been overemphasized by the press.

Brady said he had not gone to the White House today with the intention of putting down Bushnell. Other high White House officials generally agreed with this but also expressed approval of what Brady had said.

Last week, however, Deputy Press Secretary Karna Small referred reporters who asked about El Salvador to the Bushnell briefing, which was presumed to be set up after consultation with White House officials. Brady said yesterday that the briefing was not initiated by the White House, as far as he knew.

Also yesterday, in a rare give-and-take session over budget proposals, Reagan answered questions for a half-hour from women members of Congress of both parties after a lunch in the White House family dining room. The discussion was polite but spirited, particularly when Rep. Cardiss Collins (D-Ill.), a past chairman of the Congressional Black Caucus, told the president that women and children on welfare would be principal victims of the budget cuts.

Reagan said that the impact of the cuts had been distorted by their critics and reaffirmed his statements that the "truly needy" would not be removed from the rolls.

"If you give me the promise you won't hurt the poor, I'll sit down right now," Collins said to the president.

"We won't hurt the poor," Reagan replied.

Republicans were, predictably, generally more supportive of the president than the Democrats. But one Republican, Virginia Smith of Nebraska, while praising the Reagan economic policy, offered a caution against "foreign entanglements." And Rep. Margaret Roukema (R-N.J.), another supporter of the Reagan economic plan, said her constituents were critical of the large increase in the defense budget.

In other development at the White House, a Marine Guard in dress uniform appeared at the entrance of the White House lobby. It was the restoration of a custom that ended the day Richard M. Nixon left the presidency.

An aide said the guard was posted "to provide proper attention and courtesy to visitors of the president."