Two top White House advisers yesterday told restive conservatives that President Reagan remains deeply committed to conservative principles and desperately needs their help to "maintain the momentum" of his first year in office.

The assurances, from presidential counselor Edwin Meese III and chief of staff James A. Baker III, came the day after 45 conservative leaders charged that Reagan had squandered opportunities to turn the nation sharply to the right.

The two advisers pointedly avoided mention of the critique in their appearance before several hundred wealthy contributors to conservative causes. "We wanted to accent the positive," Baker said later.

Meese and Baker lavishly praised Reagan's legislative accomplishments during 1981, boasted that he had brought inflation under control and predicted that the economy would begin to recover later this year. They also warned of efforts to undercut the president's program this year.

"The bottom line is this president is going to stick with his program," Baker said at a meeting at the Sheraton Washington Hotel. "There's going to be no vacillation, no pulling back. There's going to be no change of course."

Strong conservative support will be needed to withstand "a big move this year to cut back on defense spending," Meese said. "We can't let that happen."

He also said that if conservatives ever hope to balance the federal budget, which could post a record $100 billion deficit next year, "it is essential we take on open-ended spending programs which the liberals call entitlement programs."

Although unspecified Reagan aides were roundly denounced Thursday in the critique by conservative leaders, Baker and Meese received standing ovations yesterday.

The only really hostile question was on school prayer. Why, Baker was asked, hadn't Reagan done anything about restoring prayer in public schools?

Admitting "that's one of the 40" unkept Reagan campaign promises, the White House chief of staff said, "The president continues to speak out on that. He continues to support that."

Baker also tried to dispel criticism from conservatives about the administration's successful attempts to avoid legislative battles over such social issues as abortion and school busing.

"The president holds these views, which he enunciated during the campaign, and he holds them very intensely," Baker said. But he added that Reagan had made economic recovery and strengthening national defense his top priorities, and will continue to concentrate on them.

Paul Weyrich, one of the spokesmen for the 45 conservatives who criticized the administration, said he was disappointed in the presentations by Baker and Meese. "They really didn't address the issues we raised," he said. "They ignored them."

Conservatives did get one concession from the pair. Meese said he has scheduled a meeting with Sen. Paul Laxalt (R-Nev.) on a proposed "family protection" act, "and I think you very shortly will see support for that bill" from the president.

The "family protection" act is a tidy wish list of issues raised by New Right conservatives, ranging from legalizing school prayer to providing tax breaks for adoption.

Yesterday's meeting was sponsored by several New Right conservative groups, including the National Conservative Political Action Committee and the Fund for a Conservative Majority.

In a panel session, Russell Hemenway, executive director of the National Committee for an Effective Congress, a liberal Democratic group, sharply attacked these groups for political extremism. He said they have created a political backlash that will lead to the defeat of conservative congressional candidates this year.

"If we are extremists, so is Ronald Reagan. If we are extremists, so is the Republican platform," replied NCPAC chairman John T. (Terry) Dolan.