Postal workers at Royal Mail have begun a wave of strikes that will stretch until Christmas Eve amid a bitter dispute over pay and conditions.
The walkouts will hit deliveries across the UK, Royal Mail said.
Members of the CWU union will now strike on 9, 11, 14, 15, 23 and 24 December after negotiations between the union and Royal Mail broke down.
Last week customers were advised by the postal service to post Christmas mail earlier than usual due to the strikes.
The union has said its members want a pay rise that matches the cost of living.
It warned of a “Christmas meltdown” in parcel and letter deliveries, and said millions of items of mail had been stacking up before the strikes.
The union told the BBC that management want to “force through thousands of compulsory redundancies”.
Dave Ward, CWU general secretary, said: “Royal Mail bosses are risking a Christmas meltdown because of their stubborn refusal to treat their employees with respect.
“Postal workers want to get on with serving the communities they belong to, delivering Christmas gifts and tackling the backlog from recent weeks.
“But they know their value, and they will not meekly accept the casualisation of their jobs, the destruction of their conditions and the impoverishment of their families.”
Talks have broken down between the union and Royal Mail, a spokesman said, adding that Royal Mail managers are “refusing to budge with their ‘best and final’ offer”.
That offer includes a 9% pay deal over 18 months and “a number of other concessions to terms and agreements”, Royal Mail said.
A Royal Mail spokesman said: “We spent three more days at [conciliation service] Acas this week to discuss what needs to happen for the strikes to be lifted.
“In the end, all we received was another request for more pay, without the changes needed to fund the pay offer,” the spokesman said, adding that the union “knows full well” that the business is losing more than £1m a day.
He added that the strike action had cost staff £1,200 each. “The money allocated to the pay deal risks being eaten away by the costs of further strike action,” he said.
The spokesman added that CWU was “deliberately holding Christmas to ransom for our customers, businesses and families across the country”.
He said Royal Mail was “doing everything we can to deliver Christmas for our customers and settle this dispute” by continuing deliveries, but “the task becomes more challenging as Christmas nears”.
The company has announced plans to cut up to 10,000 jobs.
