D.C. City Council chairman Arrington Dixon, accusing Mayor Marion Barry of "an expensive political stunt," yesterday said the city's renegotiated contract with city police officers is an "illegal" document that the council will refuse to recognize as a binding agreement.

In an unusually harsh letter to Barry, the council chairman angrily charged that the mayor had exceeded his legal authority and made a "mockery of the collective bargaining process" by renegotiating a new contract with Local 442 of the International Brotherhood of Police Officers only weeks after an earlier two-tiered bonus and salary plan went into effect for the District's police.

The new, more expensive contract would give the police a 20-to-22 percent pay raise over the next three years. It would replace the previous agreement that calls for a $500 bonus for the department's approximately 3,300 officers in each of the first two years of the pact and a 7-to-9 percent pay increase in the third year. About 100 police officers have filed suit in D.C. Superior Court seeking to force the city to pay the $500 bonuses.

Under the new agreement, the salary increases would become part of the officers' base pay and would be used in computing future salary increases and pension benefits. City budget director Gladys W. Mack said she does not know how much more the new agreement will cost the city.

"It's just shocking," Dixon told a reporter. "If you can constantly reopen things after they've already gone into effect, when does it end? What does it do to the morale of city employes when you don't know how much your raise is going to be because the mayor is constantly changing things?"

Barry's press secretary, Annette Samuels, said the mayor considered Dixon's statement "premature" because the council chairman hadn't even been briefed on the contract's provisions. She also noted that the city's personnel law vests collective bargaining rights exclusively "in the executive branch."

"The mayor wishes Mr. Dixon had called and asked him what the facts were" before he released his letter, Samuels said.

Under the city's labor laws, the mayor can negotiate working conditions and pay scales with unions. However, the pay provisions of any contract must go to the council, which had 60 days to disapprove them.

Dixon said the earlier contract was submitted to the council for review and was not disapproved within the 60-day period. Therefore, he said, it took effect in early October. Since that contract is in effect, he said the newly negotiated pact is "illegal as far as I'm concerned."

Late yesterday, Dixon said the mayor called him and "was troubled that I was as aggressive as I was." Dixon said, however, that he refused to back down. The council chairman also said the mayor explicitly referred to "the political benefits" Barry would gain from renegotiating contracts as the preliminary maneuvering starts for next year's mayoral campaign.

Behind the contract dispute is a bitter rivalry between two competing police groups, the IBPO and the Fraternal Order of Police, over who will serve as bargaining agent for the city's police officers. The FOP has charged that Barry and the IBPO signed the new agreement in an attempt to head off the FOP's union representation challenge.

Dixon's letter yesterday charged that it was "clearly unlawful" for the city to support one bargaining agent over another. He also expressed concern over the impact the new contract would have on about a dozen other contract negotiations the city is conducting.