WASHINGTON--The prosecutor in Michael K. Deaver's perjury trial said yesterday the former presidential aide's conviction is only a "thumb in the dike" against the flood of influence peddling in Washington.

"The successful outcome of the Deaver trial should not be mistaken as a resolution of the more serious problem which brought about the appointment of an independent counsel in the first place," Whitney North Seymour Jr. said in a statement.

"That problem is too much `loose' money and too little concern in Washington about ethics in government," Seymour said in a statement referring to "vast sums of money" spent by corporations and foreign governments "to buy influence and favors."

Seymour said that "until the attitudes of government leaders change, there is little that prosecutors can do except put a thumb in the dike."

Without naming the secretary of state by name, Seymour criticized George Shultz for vouching for Deaver's honesty and integrity when he testified as a prosecution witness.

Seymour said Shultz demonstrated a lack of leadership among public officials to improve ethics.

"The present level of that leadership has been evident during the Deaver trial itself, as the third-highest ranking official in the U.S. government willingly and publicly endorsed the honesty of a former high official, charged with perjury, without even bothering to read the indictment or inquire whether the charges had substance," Seymour said in a reference to Shultz's testimony.

The prosecutor had erupted in anger during the trial when Shultz steadfastly defended Deaver's integrity. The secretary testified that Deaver contacted him on behalf of a lobbying client but lauded Deaver's "very direct, honest approach."

Deaver, one President Reagan's closest and oldest political associates, was convicted Wednesday of lying to a House subcommittee and a grand jury that investigated the propriety of the lobbying he did for highpaying clients after he resigned as deputy White House chief of staff.

Within nine months of leaving the White House, Deaver and his firm had signed more than $3 million worth of lobbying contracts with large corporations and several foreign governments.

Deaver was not charged with violating the ethics law itself. Seymour argued to jurors that Deaver's false testimony "blocked the investigation into that."

During the trial, Seymour charged that Deaver had lied to spare Reagan and his wife, Nancy, any embarrassment from revelations that he was using his White House connections to sign six-figure lobbying contracts.

In his statement, Seymour attacked loopholes in the Ethics in Government Act that "serve only to breed cynicism by making `lawful' what otherwise would plainly be improper," Seymour said.

These loopholes technically allowed many of the contacts that Deaver made within the White House.