SACRAMENTO -- Attorney General Bill Lockyer won support from the state Senate on Monday in his battle with the politically powerful prison guards' union, as senators approved a bill that would overturn a portion of the union's contract.

Meanwhile, several Senate Democrats said they would call Tuesday for the Legislature to block the guards' lucrative pay raises.

Lockyer is contesting a portion of the contract that requires investigators to turn over confidential information to prison employees who are under investigation for wrongdoing.

The attorney general contends the provision violates other state laws protecting the confidentiality of criminal investigations. An arbitrator recently declined to rule on the provision.

"It's like playing a high-stakes game of poker and showing your opponent your hand before placing the bet," said Sen. Gloria Romero, D-Los Angeles.

The bill prohibiting the practice is one of several reform measures sought by Romero, who chairs a prison oversight committee.

Lance Corcoran, vice president of the union, the California Correctional Peace Officers Association, said the disclosure requirement is designed to help resolve complaints against prison employees quickly and as cheaply as possible. Ending the provision would sharply drive up lawsuit and settlement costs, he said.

Critics say the disclosure requirement makes it more difficult to conduct investigations of prison conditions.

Those probes are also hampered by a "code of silence" among adult and youth prison employees that protects wrongdoers while punishing whistleblowers, according to a series of national experts' reports, a scathing review by a federal court-appointed monitor and Senate hearing witnesses.

Though Romero's bill was approved by the Senate on a 32-0 vote, Corcoran said the union will try to make its case against the measure in the Assembly.

The contract's pay increase provisions also are drawing renewed fire.

Gov. Arnold Schwarzenegger, in last week's revised budget proposal, called for shaving $300 million off the cost of the contract by trimming salary increases along with overtime and sick leave costs.

He also made it easier for legislators to block the raises by making it a separate item in his budget plan.

Sen. Jackie Speier, D-Daly City, who with Romero has chaired several prison oversight hearings, has support from about a dozen Senate Democrats to block funding for the raises this year, a spokeswoman said Monday.

Speier and other senators planned to hold a news conference Tuesday to announce the pledge, which they said would send "a strong message" that the union must renegotiate its contract.

Corcoran said the senators' stand "may be a bit premature, in that we are in discussions with the administration and we may be able to work out something. It continues to be an uphill battle, but we remain hopeful."

The issue could surface before a Senate budget subcommittee Wednesday.

New Senate Republican leader Dick Ackerman of Fullerton is a member of that committee. Republicans, he said, want to renegotiate each of the states' labor contracts signed by former Democratic Gov. Gray Davis to save the combined $465 million sought by Schwarzenegger.

"If we're going to do it, if we're going to be fair, we ought to look at all of them," Ackerman said.