Mayor Edward Koch said yesterday that Queens Borough President Donald Manes, recovering from a suicide attempt, is corrupt and should be jailed along with a lawyer who implicated him in a growing bribery scandal.

"I am convinced now that he engaged in being a crook," said Koch, a close friend of the four-term borough president, the day after calling for Manes' immediate resignation.

Manes' attorney, Michael Armstrong, declined to comment on whether his client -- recovering at home from a slashed wrist and ankle -- would resign.

Koch's comments came amid reports that a third collection agency owner is due to meet with federal authorities investigating payoffs rooted in the city Parking Violations Bureau.

The two other collection agency executives cooperating with authorities are Bernard Sandow, president of Systematic Recovery Service Inc., and Michael Dowd, a Queens attorney who is a partner in Computrace Ltd.

Koch said he was deeply disturbed by Dowd's charges that he was forced to pay Manes $36,000 to secure scofflaw contracts with the Parking Violations Bureau. He said his friendship with Manes may be "permanently impaired."

"I feel violated. I feel as though a friend had assaulted me physically," Koch said.

"The two of them should ultimately go to jail," Koch said.