British Gas engineers have started a fresh wave of strikes in their dispute over pay and conditions amid warnings of a “complete breakdown” in industrial relations at the company.

Members of the GMB will be on strike for the next four days, having already taken eight days of industrial action this month in protest at new contracts.

The union warned that the action is causing a huge backlog of appointments, but British Gas said it has contingency plans in place.

GMB national officer Justin Bowden said: “The strikes provoked by British Gas leave more than 150,000 homes in a backlog for services and 200,000 planned annual service visits were axed in January.

“Field engineers have decisively rejected the new contracts with eight strike days against it.

“A lethal mix of deceit, a failure to grasp reality and wishful thinking that engineers will acquiesce on pay 15% below agreed rates and other changes has led to a complete breakdown in industrial relations between British Gas and the field engineers’ bargaining group.

“Sadly there is no respite in store for customers or staff because British Gas fails to accept that the only way to end the dispute with the engineers’ bargaining group is to take ‘fire and rehire’ off the table.”

A company spokesman said: “Our business needs to change to survive and protect 20,000 jobs. We know change is difficult but we have offered a fair deal that has been negotiated over 300 hours with unions, where base pay and pensions are protected.

“Using dismissal and re-engagement is genuinely and has always been a final resort option. That’s why we have worked so hard to ensure that it has now been removed for a significant majority of our employees – 83% have already agreed to the new terms.”

There is no sign of the deadlock being broken.

Union and company officials, including Chris O’Shea, chief executive of British Gas owner Centrica, will be questioned next Tuesday by MPs on the Business Select Committee.