Edward C. Schmults, the former deputy legal counsel to President Ford nominated to be deputy attorney general, yesterday took himself out of the federal government's antitrust case against AT&T, removing the nation's top two law enforcement officers from the case.

"I will not be able to participate in any decision on that case," Schmults told the Senate Judiciary Committee at his confirmation hearing.

The committee later voted 13 to 0 to approve Schmults' nomination, sending it to the full Senate for action.

While he did not explain it to the committee, Schmults said in a telephone interview yesterday that he could not involve himself in AT&T matters because he had brought AT&T in as a client to the New York law firm of White & Case where he was a partner.

"It happened about six or eight months ago," Schmults said. "It was a pension case that had nothing to do with the antitrust case, but it still disqualifies me from participating in any case involving AT&T."

Attorney General William French Smith already had taken himself out of the AT&T case on the grounds that he had been a director of Pacific Telephone & Telegraph, an AT&T subsidiary. This means that all decisions on the AT&T antitrust case will have to be made either by the associate attorney general or the assistant attorney general in charge of the Antitrust Division, neither one of which has been nominated yet.

"We have not made a decision yet on who will handle the AT&T matter," Schmults said.

A decision will have to be made soon since U.S. District Court Judge Harold Green last week ordered the Justice Department and AT&T to settle the government's antitrust suit against the Bell System by March 2 or go to trial two days later. Green said the parties in the six-year-old suit to break up AT&T had pledged to settle the suit by the time the Reagan administration came to power.

Schmults was asked if he and Smith planned to have two associate attorneys general instead of one, and he replied that the plan was still under study. The plan would put one in charge of criminal activities, the other in charge of civil affairs.

Like Smith, Schmults conceded he was a member of two private clubs that excluded women and, also like Smith, said he did not intend to resign his memberships because of it.