LOS ANGELES  — Attorneys for California U.S. Sen. Dianne Feinstein, the oldest member of Congress who has been beset with serious health problems, assert in a court filing that she is being stiffed on payments for “significant” medical bills by a trust created for her benefit by her wealthy late husband.

Trustees for the fund said they were “perplexed” by the filing and they have never denied any disbursement for the 90-year-old Feinstein, who was absent from the Senate for two-and-a-half months this year as she contended with shingles and other complications, including a brief bout of encephalitis.

In the Monday petition in San Francisco Superior Court, attorneys for the Democratic senator and her daughter, Katherine Feinstein, wrote that the longtime lawmaker had built up “significant” medical expenses and sought reimbursement from the marital trust, which was established in 1996 by her husband, investor Richard Blum, who died last year. The senator is the “sole income beneficiary” of the trust, which has assets that include a life insurance policy and its proceeds, the filing says.

Despite Blum’s intent to provide for his wife’s welfare after his death “the purported trustees have refused to make distributions to reimburse Sen. Feinstein’s medical expenses,” they wrote.

Additionally, they said “purported trustees” Mark R. Klein and Marc Scholvinck were not appointed in compliance with terms of the trust. The senator wants to appoint her daughter to manage the fund, which they asked the court to confirm. Katherine Feinstein is Blum’s stepdaughter.

In response, Steven P. Braccini, an attorney for Klein and Scholvinck, said in a statement, “My clients are perplexed by this filing. Richard Blum’s trust has never denied any disbursement to Sen. Feinstein, let alone for medical expenses.”

“While my clients are deeply concerned, we all remain hopeful that this is simply a misunderstanding that can be quickly resolved,” he said.

Questions Over Feinstein Granting Power of Attorney

In the filing, Katherine Feinstein, a San Francisco Fire Commission member and former judge, is identified as “attorney in fact” for the senator, which is someone authorized to act on behalf of another person.

But Braccini said, “We have not been presented with any evidence showing that Katherine Feinstein has power of attorney for her mother; nor has Katherine made it clear, either in this filing or directly to my clients, why a sitting United States senator would require someone to have power of attorney over her.”

The senator’s spokesman, Adam Russell, said in an email that Feinstein and her office would have no comment on what he called “a private legal matter.”

Feinstein is covered by Medicare and the DC Health Link, which provides health plans for members of Congress.

Feinstein, whose groundbreaking political career shattered gender barriers from San Francisco’s City Hall to the corridors of Capitol Hill, announced in February that she would not seek reelection.

After her sick leave, Feinstein returned to the Capitol in May looking noticeably thinner and frail, about 10 weeks after being diagnosed with and briefly hospitalized for shingles in San Francisco. One side of her face was drooping, apparently from Ramsay Hunt syndrome, which can occur when the shingles virus reaches a facial nerve near the ears. It also can cause hearing loss.

Other side effects from the virus include vision and balance problems. She has been using a wheelchair to get to her office and committee meetings.

Feinstein has faced questions about her memory and cognitive abilities for years — though she defended her effectiveness — and has appeared confused at times during brief discussions with reporters.

Despite calls from some in her own party to resign, Feinstein has given no indication that she is considering stepping down.