The CWU, which represents more than 115,000 postal workers at Royal Mail, has said workers will strike on Nov. 24 and Nov. 25, the bargain shopping day known as Black Friday, as well as on Nov. 30 and Dec. 1.

The two sides began talks last week aimed at resolving the long-running dispute over pay and changes to working patterns.

"The talks, which had been scheduled to conclude on 15 November, are continuing to allow more time for a resolution to be reached," a Royal Mail spokesperson said.

"But time is tight given the notified strikes starting on 24 November. If these strikes go ahead, they will cause more damage to the business and make our improved 9% pay offer over two years less affordable."

Royal Mail, the British arm of parent International Distribution Services (IDS) (IDSI.L), last month said it could cut up to 10,000 jobs and warned of more layoffs if planned strikes go ahead, flagging deeper losses this year.

"While the union recognises progress in recent negotiations has been made in some aspects, Royal Mail management failed to put any commitments into writing. Talks will now continue," the CWU said.