Firefighters are to strike on Christmas Eve and New Year's Eve and launch a ban on overtime in an escalation of their long-running dispute with the Government over pensions.
Members of the Fire Brigades Union (FBU) in England and Wales will walk out for five hours from 7pm on December 24, for six hours from 6.30pm on December 31 and for two hours from 6.30am on January 3.
FBU members in Scotland will also join the industrial action for the first time since the row flared, by joining a ban on overtime.
Between 7pm on December 27 and 7pm on the 29th, all firefighters in the union across England, Wales and Scotland will refuse to work voluntary overtime.
It will be the first time firefighters in the three nations will be taking industrial action in the bitter row over retirement age and pensions.
FBU members in England and Wales stopped work on Friday and Saturday evenings, so after the new walkouts, the union will have staged nine separate strikes since September.
FBU general secretary Matt Wrack said: "Firefighters provide a first-class standard of service 24 hours a day, 365 days a year, and these strikes will remind Government just how reliant they are on our members' professionalism, commitment and flexibility.
"However, there should be no need for industrial action, and it's absurd that firefighters' concerns over pensions have not been addressed already.
"The Government must stop claiming they are negotiating when they have refused to talk for two months and insist on forcing through proposals that are unaffordable, unworkable and unfair.
"By simply conceding common sense and allowing firefighters a fair deal, the Government could end this industrial action today."
The union has been arguing that firefighters in their late 50s face the prospect of being sacked or seeing their pension reduced by almost half because of changes in the retirement age.
Negotiations have been continuing in Scotland, making enough progress to avert strikes, but the union said no settlement had been made.
The FBU said firefighters' pension schemes are among the most expensive for workers anywhere in the public or private sector, but among the cheapest proportionally for the Government.
Most firefighters, who take home approximately £1,650 a month, already pay £320 or more a month into their pensions, and from next April this would rise for the third year in a row to more than £340 a month (£4,000 a year), with many facing a fourth consecutive rise of 2.2% in 2015, said the FBU.
The union claims that the Government's proposals are "designed to fail" because they ignore the physical demands and fitness standards required by the occupation.
"Evidence suggests that at least two-thirds of the current workforce will face dismissal or their pension reduced by almost half because they are unable to maintain the fitness standards required by the fire service beyond the age of 55," said the FBU.
Meanwhile, investigations are continuing into the death of a man in a fire in London which broke out during the last strike on Saturday evening.
London Fire Commissioner Ron Dobson, said: "As with the previous six strikes we will once again be putting our contingency arrangements in place.
"I very much hope that the Government and FBU are able to resolve this dispute soon in order that the Brigade can return to business as usual."
As in previous strikes, the London Brigade said it will have 27 fire engines based at strategic locations and contingency crews will deal with emergencies across the capital during the new strikes.
Fire Minister Brandon Lewis said: "The decision by FBU leaders to interrupt the Christmas holiday season with unnecessary industrial action is completely cynical.
"I met with the FBU on December 4 to continue discussions but their actions today show that they are not serious about resolving this dispute, which simply further damages firefighters' standing with the public.
"The deal on the table gives firefighters one of the most generous pension schemes in all the public sector. A firefighter who earns £29,000, and retires after a full career aged 60, will get a £19,000 a year pension, rising to £26,000 with the state pension. An equivalent private pension pot would be worth over half a million pounds and require fire-fighters to contribute twice as much.
"I would like to reassure the public that there are robust contingency arrangements in place."