Sol M. Linowitz, co-chairman of the U.S. team negotiating a new Panama Canal treaty, resigned from the board of Marine Midland Bank of New York this week after questions of conflicts of interest were raised by legislators.

"He's done this to avoid any implications of conflict that might affect ratification of a new treaty," said Ambler Moss, an aide to Linowitz.

Linowitz, who is co-chairman with Ambassodor Ellsworth Bunker, was criticized Feb. 21 for retaining his private business intests by Sen. Jesse Helms (R-N-C.).

This week, Sen. James A. McClure and Rep. George V. Hansen, both Idaho Republicans, filed suit to force Linowitz to go through congressional confirmation proceedings. They asked that his paycheck be withheld.

Linowitz will serve for six months on the negotiating team, which means he is not subject to conformation hearings. Moreover, he is serving without pay, according to Moss.

Linowitz, who was ambassador to the Organization of American States under President Johnson, is a senior partner in the Washington office of Coudert Bros., a New York law firm.

He is on the board of directors of Pan American World Airways, Inc., among other companies.

Helms, who like the two other legislators favors taking a hard line in negotiations with the government of president Omar Torrijos, said in a Senate floor speech: "It seems to me a grave error to have a banker who is in bed with Torrijos negotiate the proposed treaty."

Marine Midland has a $4 million share of a $115 million loan made to Panama in 1973 by a international consortium. The first payment is due next year.

Helms also questioned Linowitz's directorship of Pan Am, whose planes service Panama.

Michale Kozak, an attorney with the State Department, said that when Linowitz was considering the appointment, he was "very forthcoming about all his interests."

State Department attorneys said he could remain on the bank board, but this eek Linowitz resigned to "remove even the slightest suggestion of a conflict of interest." He has not quit the Pan Am board."

"If we go into any aviation issues in our negotitions, said Kozak, "Linowitz said he would exclude himself from the negotaitions."

The State Department did find two conflicts of interest among Linowitz' financial affairs. Kozak said. Linowitz had a "very minimal number" of shares in American Telephone & Telegraph Co., and Texaco, Inc.

Because Texaco fuels ships in the canal and AT&T has an interest in a cable passing through the canal, State suggested Linowitz sell those shares. "He divested himself of the stock prior to taking the appointment," said Kozak.

State got assurances from Linowitz' law firm that it does not have clients involved with Panama, and that it will not acquire any so long as Linowitz is a negotiator.