Labor unions that have solidly backed President Obama are splitting with him over ObamaCare — with one calling for the “repeal or complete reform” of the president’s signature health-care law.

Union leaders argue insurance costs for millions of workers will increase under the president’s health-care plan so they might have to drop their existing plan, despite Obama promising the opposite.

Their primary concern is the multi-employer or so-called Taft-Hartley plans that cover unionized workers in retail, construction, transportation and other industries that frequently use seasonal and temporary employment.

The union leaders say the roughly 20 million people covered by the plans will likely have higher premiums because the Affordable Care Act does not include tax subsidies for them.

However, workers seeking coverage in the upcoming, state-based marketplaces for insurance, known as exchanges, can qualify for subsidies.