Strikes due to begin at six additional Tesco stores from Monday will be deferred until next Friday because of alleged flaws in the way the Mandate trade union served notice of industrial action on the company. 

Tesco and Mandate are engaged in a dispute over the transfer of around 250 of its 14,000 employees to less-favourable contracts.

Some 1,500 employees at 16 stores are already on strike, and a further 500 based in six more stores were due to join the industrial action from Monday.

The six stores were due to join the strike between Monday and Wednesday.

However, a spokesperson for Mandate confirmed that lawyers for Tesco had challenged the validity of next week's strike notice served by the union.

The spokesperson said that Mandate did not accept that there was any flaw in the strike notice.

However, he said to avoid any risk of being tied up in expensive legal proceedings, the union had decided to re-serve the seven-day strike notice to take effect tomorrow week.

Mandate has balloted members in 45 stores for industrial action, with 22 backing it, but 23 rejecting it.

Tesco has described the strike as unjustified and irresponsible, and has urged the union to accept a Labour Court recommendation aimed at resolving the dispute, which has been rejected by members.

Originally around 1,000 Tesco staff were affected by the move to alter contracts, but the company has spent over €73m on redundancy payments for 700 of those employees to leave the company.