Senate Majority Leader Howard H. Baker Jr. (R-Tenn.), who spearheaded the congressional fight for President Reagan's cuts in domestic programs, said yesterday the cuts may have been excessive and urged a new focus on tax increases, defense cuts and retrenchment in benefit entitlement programs.

Coming on the heels of similar signals from other Republican leaders, it was the strongest message yet from Congress that Reagan faces deep trouble if he pursues further cuts in domestic appropriations as part of his fiscal 1983 budget offensive.

Recommendations for such cuts from Reagan's Office of Management and Budget have also prompted protests from several Cabinet secretaries and are under review by the president.

"I agree with Mark Hatfield the Senate Appropriations Committee chairman and others who say that you've cut all you can cut for all practical effect from discretionary programs," Baker told a group of Gannett newspaper executives in an interview that was recorded and circulated by Baker's office.

"And there may be some of them that you may have to go back to and repair some of the damage that's been done," Baker continued. "We may have overdone it already in some of them. But if you're going to do that, and still trim those deficits, you are going to have to go back and pick up some money somewhere."

Similar comments have been made in recent days by Sen. Paul Laxalt (R-Nev.), Reagan's closest friend in Congress, and by Senate Budget Committee Chairman Pete V. Domenici (R-N.M.), who renewed his campaign for tax increases and cuts in benefit programs yesterday in an interview on ABC's "Good Morning America."

"I don't believe we can get where we ought to be if we just cut those discretionary appropriations that we've been hearing so much about--that is, Head Start, community development, some additional cuts in highway construction and the like," said Domenici in a reference to some of the OMB proposals. "That's not a big enough part of the budget."

Both Domenici and Baker said tax revenues can be increased without touching the huge tax cuts that Congress enacted last summer for individuals and businesses. They suggested raising excise taxes, such as those on tobacco and alcohol, and closing tax "loopholes."

Baker also renewed his proposal for a "windfall profits tax" on the proceeds from deregulation of natural gas prices but added this caveat:

"There's just one little problem with that, and that is that the president of the United States isn't for it. I don't know whether you can argue him out of that or not. I tried the other day . . . and he said in characteristic kindness, 'But, Howard, you should remember that I am president and you are not.' "

Baker also went beyond his previous budget stance in urging major savings from defense and benefit entitlement programs.

While supporting all of Reagan's proposed new weapons systems, "I simply cannot believe that out of a budget as large as the Pentagon budget, that we can't find 5 billion or maybe even 10 billion dollars that we can save if we really put our minds to it, without affecting the quality of our national defense . . . ," he said. Reagan earlier this year proposed $5 billion in defense savings for 1983.

Baker acknowledged that Reagan has put Social Security off limits for cuts next year but said there are 26 other benefit programs, making up 60 percent of the budget, that could be cut. "And even if it makes only a slight savings in the total budget deficit . . . , he Reagan has to commit to the idea of entitlement changes," Baker added.

As Congress struggled to adjourn for the year by mid-week, both houses approved a transportation appropriations bill and sent it to Reagan. But the Senate bogged down over the Treasury-Post Office money bill as it was confronted by threats of a filibuster over a proposal for strict new limits on abortion payments in federal workers' health plans.