SAINSBURY’S enraged unions and MPs yesterday by refusing to back down in a row over staff pay linked to its attempted £12 billion merger with Asda.

Unite officer Joe Clarke accused the supermarket chain of “holding a gun to workers’ heads” by threatening them with the sack if they refuse to sign new contracts that start in September.

The union is seeking legal advice, saying the firm has failed to consult staff meaningfully.

More than 100 MPs criticised Sainsbury’s for using an increase in its basic wages as a “smokescreen” for the erosion of workers’ benefits such as paid breaks and a premium rates on Sundays.

Basic pay will rise from £8 to £9.20 per hour, but employees will no longer be eligible for a bonus.

Sainsbury’s sought to quell the backlash yesterday by saying that talks with its staff had been completed and it would invest an extra £10 million in its proposed pay rates.

It wrote to MPs to defend its proposals, but Labour’s Siobhain McDonagh said she believed the plans would still leave 9,000 workers worse off.