METHUEN, Mass. – More than 300 unionized workers at Shaw’s supermarkets’ distribution center in Methuen have gone on strike after rejecting what they call an “unjust and inequitable” contract offer.

A spokesman for the United Food and Commercial Workers Union Local 791 said Shaw’s offer included increases in health care contributions and “substandard” wage increases that would result in a net loss of money for members over the term of the contract.

The West Bridgewater-based supermarket chain said in a statement that it was “disappointed” with the rejection of “our last, best and final offer” that included “minimal” health care increases.

The Methuen facility distributes meats, dairy products, produce and other perishables to Shaw’s and Star Markets throughout New England.

The chain has been a wholly owned subsidiary of J. Sainsbury plc of London since 1987.