British Gas engineers are to stage a series of fresh strikes in a dispute over pay and conditions.
Members of the GMB union will walk out for 24 hours on January 20, 22, 25 and 29 and February 1.
The announcement was made at the end of a five-day stoppage by thousands of engineers whose jobs include servicing boilers.
They previously voted by 9-1 in favour of industrial action in protest at changes to their pay and conditions.
The last strike involved around 4,500 service and repair gas engineers, 600 central heating installers, 540 electrical engineers, 170 specialist business gas engineers and 1,700 smart metering engineers.
British Gas maintains it is trying to protect jobs, insisting basic pay and pensions are being protected.
The GMB also launched a national strike fund with an appeal to its branches and members.
National officer Justin Bowden said: “A profitable British Gas provoked their loyal staff into strike action in the depths of winter by refusing to heed their overwhelming rejection of the fire and rehire pay cuts.
“They have now ignored a five-day demonstration by the engineers that the proposals are not acceptable.
“They are forcing further disruption on their customers all the way into next month because of the new strike dates.
“British Gas should recognise that the only way to end the disruption they provoked is to take fire and rehire pay cuts off the table.”
A spokesman for British Gas parent firm Centrica said: “We’ve done everything we can with the GMB to avoid industrial action.
“Whilst we’ve made great progress with our other unions, sadly the GMB leadership seems intent on causing disruption to customers during the coldest weekend of the year, amid a global health crisis and in the middle of a national lockdown.
“We have strong contingency plans in place to ensure we will still be there for customers who really need us, and we’ll prioritise vulnerable households and emergencies.
“Over 83% of our workforce have already accepted our new terms, in which base pay and pensions are protected, including a significant majority of GMB members.
“This shows most of our people understand that our business needs to change because customer needs are changing.
“GMB’s mandate for strike action is weak. They are fighting against modernisation and changes which will help to protect well-paid jobs in the long term and are doing so at a time that our country needs everyone to pull together.”