Staff at 70 Tesco stores nationwide are to begin an indefinite strike tomorrow over disagreements about contracts.

The company is proposing changes to the working conditions of long-serving staff that will see a reduction in their pay.

Tesco has said it is extremely disappointed with the decision as it has yet to implement planned changes to the contracts of 300 staff.

Assistant general secretary of Mandate Gerry Light said there is a possibility the stores hit by strike action will have to close.

“70 stores (will see strike action) tomorrow and from tomorrow there will be a process of engagement with the rest of the stores to ascertain whether they are going to engage in supportive action down the line,” said Light.

“I think in the past what we have seen that the workers have always been supportive of official picket lines when they are placed on their place of employment.”