Two powerful New York labor unions are fighting — not for their members but over them, The Post has learned.

Workers United — a local chapter of the powerful Service Employees International Union (SEIU) — is trying to poach 300 workers from the International Longshoremen’s Association, who provide laundry services to Manhattan’s luxury hotels, the Longshoreman’s union charges.

ILA Local 1964 has for years represented workers at the Bronx-based Carnegie Linen Services and Valet Cleaning Corp., whose client list includes the Waldorf-Astoria. But Workers United is trying to organize workers there in one of the city’s ugliest union vs. union disputes.

“It’s avarice. It’s greed. It’s very un-labor-like. It’s easier to steal workers who already organized than to organize the unorganized,” Local 1964 lawyer Bryan McCarthy said in slamming Workers United.

Workers United fired back that the ILA is a toady for a company it claims mistreats and underpays its workers.

“Local 1964 is helping an abusive employer run a sweatshop and negotiate poverty-wages and lousy benefits and workers have reached out to us for real representation. We are proud to have these industrial laundry workers fight for the higher pay, better benefits and respect they deserve,” said Workers United lead organizer Megan Chambers.

Carnegie Linen, which pays workers from $8 to $25 an hour, filed a lawsuit in Bronx state Supreme Court alleging that Workers United is trying to put it out of business by picketing in front of Manhattan hotels that are its main customers.

The feds have called for a new election to determine which union should represent Carnegie workers.