A federal class action lawsuit filed late Tuesday accuses New York State health officials of denying or slashing Medicaid home care services to chronically ill and disabled people without proper notice, the chance to appeal or even an explanation, protections required by law.

The lawsuit, filed in United States District Court for the Southern District of New York, names three plaintiffs: an impaired 84-year-old woman living alone in Manhattan, a frail 18-year-old Brooklyn man with severe congenital disabilities, and a 65-year-old Manhattan man with diabetes and a schizoaffective disorder. But it was brought by the New York Legal Assistance Group on behalf of tens of thousands of disabled Medicaid beneficiaries who need home health care or help with daily tasks like bathing and eating.

It represents a challenge to an ambitious Medicaid overhaul by Gov. Andrew M. Cuomo that shifted $6 billion in public spending on long-term services, including home care, to private managed care companies that are paid a fixed sum for each enrollee. The goal of the overhaul, which was set in motion in 2011, was saving money and improving the coordination of care. But advocates for aged and disabled people have complained that in the scramble for the most lucrative enrollees, companies are shunning frail people with the greatest needs and signing up those who could be given minimal services.

The lawsuit, filed against the state commissioners of the Department of Health and the Office of…