President Reagan, in the latest of a week-long outpouring of activities on behalf of minority civil rights, signed an executive order yesterday requiring federal agencies to make official plans annually for giving contracts to minority businesses and to begin assisting minority companies to compete for federal contracts.

The president acknowledged criticism of the nonstop show of administration activity on civil rights as he signed the minority business development order in a Cabinet meeting.

He was overheard by reporters telling one of his black aides, Wendell W. Gunn, that the steps taken by the administration on civil rights this week are not intended as public relations gestures to repair his image as an opponent of minorities: "It isn't like some people say, that I'm just trying to change opinions or something."

Gunn responded, "Mr. President, you do what you think is right."

"That's what I've been trying to do," Reagan said.

The administration kept up the drumbeat on civil rights yesterday as Attorney General William French Smith met with civil rights activist Jesse L. Jackson.

Smith promised to consider Jackson's request for a conference on civil rights problems confronting blacks, particularly efforts to keep them from voting. Jackson said that 53 percent of the nation's blacks are unable to vote because of discriminatory actions.

Smith later told reporters that the Justice Department had been aggressively enforcing civil rights laws under Reagan before the recent push from the White House.

"This is not an activity that we have just discovered recently," Smith said. "We've been doing it for the last 2 1/2 years, and we certainly intend to keep doing it."

Meanwhile, Democrats on the Senate Judiciary Committee won a postponement of the vote on the president's three nominees to the U.S. Commission on Civil Rights until September. Another round of hearings on the nominations is scheduled for next week.

The postponement came over the objections of Sen. Orrin G. Hatch (R-Utah), who chaired most of the hearings Wednesday. Hatch said that another hearing was unnecessary, adding: "I sat through more than 35 witnesses with little or no participation by minority Democratic members, and there was no criticism of the nominees except that Reagan appointed them."

Hatch and Sen. Strom Thurmond (R-S.C.) controlled Wednesday's hearings, focusing them on the ability of the nominees and defending the president's right to fire commission members who do not share his opposition to quotas and busing. It appeared after the hearing that any vote on the nominees, which normally would have taken place next Thursday, would have been in support of Reagan's choices.

Next week's session will be chaired by Sen. Howard M. Metzenbaum (D-Ohio), who strongly opposes the nominations and scoffed at Reagan's actions on civil rights in the past week--asking Congress for new enforcement powers to combat housing discrimination and ordering the Justice Department to file suit against Alabama for its allegedly segregated state college system.

"Where has this administration been over the last 30 months when it really counted?" asked Metzenbaum. He added that Reagan is trying to "silence" the Civil Rights Commission by changing the composition of its membership.