Philip A. Lacovara, special counsel to the House ethics committee's investigation of South Korea influence-buying on Capitol Hill, resigned yesterday after a stinging personal attack on him by committee Chairman John J. Flynt Jr. (D-Ga.).

Flynt had picked Lacovara personally to lead the inquiry because of the reputation for ability and integrity he had earned as an assistant Watergate special prosecutor. Lacovara resigned that post in protest over Presidents Ford's pardon of Richard Nixon.

Lacovara said in a telephone interview from Bath, England, last night that he drafted a letter announcing his firm's resignation yesterday shortly after hearing reports that Flynt had questioned his integrity and attacked his motives in interviews with newspaper reporters earlier in the day.

It was not clear immediately whether other members of the committee's special staff would follow Lacovara in resigning. But his resignation seems certain to delay further the investigation which already has been criticized as slow-moving. It also seems likely that the resignation will bring charges from Republican leaders that Flynt's remarks were politically motivated.

In remarks he first made to the Atlanta Journal and later repeated to The Washington Post. Flynt said he was going to ask the General Accounting Office to audit the $35,000 bill for legal services which Lacovara's firm. Hughes, Hubbard & Reed, submitted for last month.

Flynt said he found the billing "incredible" and said he questioned the amount of time (469.5 hours) alleged in it."

"To me it's incredible they can spend that much time and complain about nothing being done." Flynt told The Post.

He claimed he didn't intend to "exacericate" the situation. "I don't think I pushed him as far as he was pusing me. I think I was restrained and cool-headed to wait for almost a week to respond to his criticism in the memos."

Flynt told the Atlanta paper that he didn't know when he hired Lacovara that he was "susceptible to temper tontrums and ego trips."

He also said he found it "difficult to believe" Lacovara's statement in a telephone call Thursday that the counsel had not sought a confrontation when he circulated two memoranda critical of Flynt's handling of the investigation to other committee members just before the July 4 recess.

Press reports about those memos earlier this week obviously had angered Flynt. He told the Post Tuesday that the memos were "inaccurate." By yesterday his characterization of the memos had escalated to where he told a Journal reporter they were "arrogant, self-serving, misleading and grossly inaccurate."

Flynt insisted, before Lacovara's resignation, however that he had no wish to fire the special counsel or force him out.

In the letter of resignation Lacovara said that "it is now evident that the relationship of mutual trust and confidence that must exist between lawyer and client to longer exists."

He said he saw no alternative but to withdraw his firm's representation of the committee.

In the phone interview from England, where he is vacationing, Lacovara added, "When a client gives interviews casting aspersions on his lawyer, it becomes obvious that the relationship can't continue.

He said he had "had the feeling for a while that it (resignation) was inevitable. things have been difficult from the beginning. At virtually every substantive phase it has been an uphill battle to convince some of the members to do what I thought was appropriate to conduct a professional investigation."

Lacovara cited delays in preparing a quationnaire to be sent to all members of the House,and the committee members" unwillingness to disclose their own acceptance of favors from foreign governments as examples.

Disagreement started to get more serious just before the July 4 recess. Lacovara said, when he couldn't get Flynt to schedule a meeting to consider a wave of subpoenas for witnesses and several applications for immunity. Flynt said he was busy with Appropriations Committee hearings.

It was then that Lacovara wrote a memo to other members, telling them, he said, of the importance of having a meeting. Flynt "orordered me not to sent it. He said if I did, either he would go, or I would go," he said.

The attorney said he didn't send the first memo because Flynt assured him that he personally could handle pending problems about an agreement with the Central Intelligence Agency for cooperation with the committee and a threatened subpoena for a document being denied the committee by the Justice Department.

Lacovara said he found out a few days later that Flynt had left town for the recess period without carrying out those two promises. So Lacovara then wrote all the committee members again and attached the first memo, criticizing Flynt's management of the pace of the inquiry.

The special counsel left on a long-planned vacation with his wife last weekend and his absence was sarcastically noted at a committee meeting Wednesday after the press accounts of his memos surfaced the day before.

That meeting was the committee's first in five weeks.

At that Wednesday meeting, Flynt announced more regular meetings. Though one veteran member, Rep. Olin E. Teague (D. Tex.) called for Lacovara's firing, other committee members seemed hopeful the disagreement would not escalate into a feud like the one between Rep. Henry B. Gonzalez (D. Tex.) and Richard Sprague, the counsel for the liouse assassinations inquiry. Sprague was forced out earlier this year after several verbal lashing from his committee chairman.

Lacovara said he called Flynt Thursday to apologize that the memos had made public and to offer to return from his vacation for next Wednesday's committee meeting.

He declined to speculate on what had prompted Flynt's personal attact, except to say. "Obviously there is a reluctance by a few members to pursue what is the uncomfortable, unpleasnat task of investigating their colleagues."

He said, "This is an important investigation that ought to be pursued. From what I've learned to date, it would be tragic for it to be discontinued."

Reaction to the resignation from other quarters varied from sadness to satisfaction. Committee member Rep. Bruce F. Caputo (R.N.Y.) the freshman who has criticized Flynt before, said through a spokesman that Lacovara's leaving was a "tremenous blow to the investigation. His credibility and reputaion in many ways is higher than the committee's."

Teague, on the other hand, said, "We shouldn't have hired him in the first place. I wouldn't have. He was making himself look good. He wanted another Watergate."

Though Lacovara has been in the public eye most often, several other members of the Hughes Hubbard & Reed firm have worked on the investigation. The firm was hired by the committee at $75 an hour, but wiuld be constantly available.