President Reagan sought last night to "set the record straight" and dispel fears that his policies discriminate against blacks. That charge "strikes at my heart every time I hear it," he said.

Speaking to the National Black Republican Council, a GOP auxiliary group, Reagan contended that his administration in fact has been more vigorous than any other in investigating and prosecuting complaints of discrimination. "Look at the record," he challenged critics.

Although the lives of the poor "are not what we'd like them to be," Reagan said, his economic program has left low-income people "better off today than if we had allowed runaway government spending, interest rates and inflation to continue ravaging the American economy."

Conceding that in the past Republicans have failed to communicate their concern for civil rights, Reagan told his Shoreham Americana audience that the GOP intended from now on to reach out to blacks and was not writing off the black vote.

The Reagan efforts so far, however, have appeared designed not so much to win black support as to calm the fears of moderate whites concerned about charges of administration racism. Blacks generally have been overwhelmingly and unbudgingly opposed to Reagan throughout his tenure in the White House.

"It's less important to win over black voters than it is to maintain an open door with the black community and to convince many whites who care about these issues that this remains the party of Lincoln," White House communications director David R. Gergen said shortly before the speech last night.

In defending his administration, Reagan made it clear that he did not intend to change course. The only new initiative in his speech was a promise to announce this month a program for developing ties between minority businesses and major corporations, and for increasing the amount of goods the federal government buys from black firms.

That commitment prompted most in the audience of 1,300 to give Reagan a standing ovation, one of many times his speech was interrupted by applause.

Although Reagan often referred to "we Republicans" in his speech, there was a heavy sprinkling of Democrats in the crowd, including Ernest Green, an assistant secretary of labor in the Carter administration, and civil rights spokesman Jesse Jackson, who campaign heavily against Reagan in 1980.

A few businessmen among the Democrats present said they attended the event not so much to hear the speech as to make contacts in the Reagan administration.

To demonstrate his administration's "solid, unshakable commitment" to civil rights, Reagan cited a battery of statistics that he said indicated unprecedented efforts to investigate and prosecute charges of violence and intimidation against blacks, violations of the Voting Rights Act and complaints of job discrimination.

A study of his administration's civil rights record by a group calling itself the Washington Council of Lawyers was released yesterday and came up with opposite conclusions, contending that the Justice Department has been transformed from civil rights advocate to "naysayer, the too-frequent adversary of minority group interests, the disrupter of continuity."

"It seemingly has gone out of its way to alienate minority groups by its actions and by its rhetoric, even in circumstances where differences have been minimal or readily resolvable," said the report, prepared with the help of top civil rights enforcers in the Carter administration.

Reagan, defending his budgets cuts, decried the social spending of the 1960s and 1970s, saying that urban renewal, for example, had been a "dismal failure" and that other efforts designed to create upward mobility had instead produced a "new kind of bondage" that trapped the poor in "welfare dependency."

If there had been no Great Society under President Johnson, he suggested, black families would be a lot better off than they are.

"With the coming of the Great Society, government began eating away at the underpinnings of the private enterprise system," Reagan said. "The big taxers and big spenders in the Congress had started a binge that would slowly change the nature of our society, and even worse, it threatened the character of our people."

As examples of his administration's concern for blacks, Reagan said civil rights enforcement agencies and black colleges had been spared deep cuts.

He also sharply attacked Congress for not acting on his proposal for urban enterprise zones, a new idea that he said "runs against their ideological obsession for even bigger and more expensive government."

"Now at a time of high unemployment and even higher black unemployment, you'd think the Congress would be anxious to move on an innovative idea to tackle such a serious national problem," he said. "Well, think again."

"Do they want the economy to remain stagnant so they can use that as a campaign issue?" Reagan asked rhetorically.

In closing, Reagan said: "No other experience in American history runs quite parallel to the black experience . . . . What our administration and our party seek is the day when the tragic side of the black legacy in America can be laid to rest for once and all, and the long, perilous voyage toward freedom, dignity and opportunity can be completed."

In a related matter yesterday, White House spokesmen said Reagan has no plans to hold a summit on black issues at Camp David, as Clarence Pendleton, chairman of the U.S. Commission on Civil Rights, had reported.

Such summits "produce more expectations than they can fulfill," a senior presidential adviser said.