Kaiser Permanente’s 2,600 California mental health clinicians are expected to begin a weeklong strike Monday to highlight what they say is inadequate staffing and long wait times for appointments.

The psychologists, therapists, counselors and social workers are represented by the National Union of Healthcare Workers. More than 700 other Kaiser workers are expected to join the strike, including Northern California optical workers and Southern California medical social workers, speech pathologists, audiologists, health educators and dietitians.

“We don’t want this strike to happen,” said union President Sal Rosselli.

If the two sides do not agree, workers are expected to walk out of more than 100 facilities throughout the state and picket 35 sites. The health care provider said it would remain open, but some appointments were being rescheduled.

Kaiser’s labor issues deepened early Friday evening when its Northern California nurses announced they would strike on Jan. 21 and 22 to protest what they say is “a growing erosion of patient care.”

Walking off the job for a week is “going to impact our patients who need our therapists to be here for them,” said John Nelson, Kaiser Permanente vice president for government relations. “We think that’s absolutely unsupportable.”

Rosselli said the union wants to bring attention to Kaiser not having enough clinicians to treat a growing number of patients seeking mental health care. State law requires a mental health patient to be seen within 10 days of asking for an appointment. But some patients have had to wait four weeks or more, he said.

The two sides have been in a labor dispute for years.

“The clinicians decided to draw the line. We want to force Kaiser to obey the law,” Rosselli said.

Kaiser has been working to reduce appointment wait times, made more difficult by a nationwide shortage of psychologists and therapists, Nelson said.

“In spite of the shortage, we’ve been able to add staff,” he said. Kaiser has hired hundreds of mental health clinicians in the past three years, Nelson said.

The union alleges wait times for appointments have worsened since Kaiser has enrolled more members under the Affordable Care Act, but Nelson disagreed.

“Since 2011, we have increased the number of therapists by 25 percent while membership has grown by 8 percent,” he said.

A state agency fined Kaiser $4 million in 2013, finding that patients often had to wait weeks to get appointments.

The state Department of Managed Health Care also said Kaiser violated state law that requires equal access for mental and physical health treatment.

The penalty was the second-largest in the department’s history. Its investigation also found Kaiser’s written description of its mental health services was complicated and misleading.

The state’s survey was done in 2012, and Kaiser has made improvements since then and the situation has gotten better, Nelson said.

“Kaiser offers among the highest quality mental health care in the nation, but we acknowledge we can do better,” he said.

The state agency’s investigation was prompted by a complaint mental health workers filed in 2011.

Kaiser also has been sued by patients over what they say is inadequate mental health treatment. One lawsuit accuses the health-care provider of telling families that seriously ill psychiatric patients need to drop Kaiser coverage in order to receive treatment through the state’s Medi-Cal program.

“We have reviewed every case extensively, and we have found no case where there’s any substance to the allegations,” Nelson said.

Contact Rebecca Parr at 510-293-2473. Follow her at Twitter.com/rdparr1.