More than 90,000 members of California’s largest union representing state employees will stage a one-day strike Dec. 5 in protest of what union officials call the government’s “unlawful” and “egregious” labor practices during contentious negotiations for a new contract.

SEIU Local 1000, which represents 95,000 state employees — including nurses, teachers, custodians and government analysts working in the majority of California’s more than 300 government agencies — announced its intention to strike Tuesday.

The Sacramento-based union’s employees voted 92 percent in favor of a strike on Nov. 15 if their demands couldn’t be met. State negotiators had offered the union an increase in pay of nearly 3 percent per year, or roughly 12 percent over four years.

In rejecting that offer, union officials criticized another condition of the proposed raise: mandatory increased employee contributions to their own retirement plans, as well as restrictions on retirement health benefits for new state hires.

The planned strike will put new pressure on Gov. Jerry Brown’s administration to give the union’s members a larger raise than officials have put on the table so far since the bargaining period opened in April.

Union leaders are timing the strike on the same day as the swearing-in of state lawmakers in Sacramento, when thousands are expected to flock to California’s capital.

Though union officials aren’t legally required to give notice of their intention to strike, they did in this case “out of concern for our families and the communities we serve,” said Yvonne Walker, president of Local 1000, in a statement.

A spokesperson for CalHR, the state agency overseeing the contract negotiations, said the agency has been “committed to bargaining in good faith” since the beginning and will continue “this process until an agreement is reached.”

Michael Bodley is a San Francisco Chronicle staff writer. Email: mbodley@sfchronicle.com. Twitter: @michael_bodley