Royal Mail workers are to stage six fresh strikes next month, including on Christmas Eve, their union has announced.
The employees are in a long-running dispute over pay, jobs and conditions.
The Communication Workers Union had already planned four days of strikes beginning next week. They are on Thursday and Friday – which is Black Friday – as well as Wednesday 30 November and Thursday 1 December.
Members will now also walk out on 9, 11, 14, 15, 23 and 24 December, the union said.
A spokesperson said: “The CWU want a negotiated settlement with Royal Mail Group and will continue to engage the company to that end.
“But those in charge of Royal Mail need to wake up and realise we won’t allow them to destroy the livelihoods of postal workers.”
A Royal Mail spokesperson said: “Our preference is for an agreement with the CWU but the change we need is not optional.
“They should be focused on a resolution to this dispute for their members and the long-term health of the business, rather than damaging strike action.”
The company says strikes will cause more damage to the business and make its 9 per cent pay offer over two years less affordable.
On 31 October, Royal Mail proposed a “pay-for-change” offer to the CWU, despite making a loss of £219m in the first half of the year.
It has been consulting on plans to cut around 10,000 full-time jobs by August. Bosses say the pay offer of 9 per cent includes a 7 per cent salary increase over two years, plus a lump sum payment of 2 per cent this year.