New owners who buy failing supermarkets won’t be allowed to fire any worker for 90 days under legislation being supported by 18 members of the City Council, The Post has learned.

The union-backed Grocery Worker Retention Act, which will get a hearing in the council’s Civil Service & Labor Committee on Friday, requires market buyers to keep current workers on the payroll during a 90-day “transition” period.

The bill’s sponsor, Daneek Miller (D-Queens), insisted the new requirement is not onerous, saying owners can still fire old employees, but only after they are given a “real trial.”