SACRAMENTO — Severe prison crowding is complicating efforts to improve California’s abysmal inmate health care system, a court-appointed receiver warned Tuesday in a report that also said any remedies will be costly.

Trimming the number of inmates would significantly reduce the cost and duration of federal intervention in the state’s prison health care system but would not solve all the problems, said Robert Sillen, the receiver who sent his report to a federal judge.

Those “who think population controls will solve California’s prison health care problems, are simply wrong,” Sillen wrote. “The cure to existing health care problems will be difficult and costly to implement, regardless of population-control efforts.”

Sillen’s 48-page report to U.S. District Judge Thelton Henderson in San Francisco comes a day before Gov. Arnold Schwarzenegger is to present Henderson with his plan to ease crowding in the nation’s largest state prison system.

More than 172,000 inmates are living in space designed for fewer than 100,000, a condition that has prompted numerous lawsuits and contributed to court decisions that have placed many prison operations under federal oversight.

Henderson and two other judges have scheduled separate hearings next month. They will consider appointing a three-judge panel that could cap the inmate population and potentially order the early release of thousands of inmates.

Attorneys advocating for inmates filed similar motions with all three judges, arguing that crowding is harming care for prisoners who have medical or mental health problems.

“We still maintain the position that nothing can get better without reducing the population,” said Don Specter, director of the nonprofit, San Francisco-based Prison Law Office.

Schwarzenegger’s plan centers on a $7.8 billion prison and county jail building program that was approved earlier this month by the Legislature. In the short term, it relies on sending thousands of inmates to private prisons in other states.

But Sillen said the plan could make it more difficult to provide inmates with proper health care if the newly constructed cell houses are built at existing prisons that already are overcrowded, especially those in remote areas.