The energy giant has been described as ‘reckless’ by union GMB as each day of strike action increases the backlog of work.

Engineers and other workers have been on strike for five days up to 11 January , for two days last week on 20 and 22 January, and on 25 January this week. There will be further strikes on 29, 30 and 31 January and 1 February.

GMB says British Gas provoked the dispute and it has resulted in a backlog of work much bigger than the company admits.

British Gas say each day of strike action means a backlog of 6,000 service jobs – but GMB says the backlog is growing at treble this figure.

The workers are in dispute over the company’s attempt to impose hourly rates 15% below agreed rates and other changes.

British Gas engineers and staff voted overwhelmingly by 89% to strike after boss of parent company Centrica, Chris O’Shea, threatened to fire them all if they didn’t accept cuts to pay and terms and conditions.

GMB says the backlog of customers waiting for service has reached a 150,000.

The first five days of strike action caused massive disruption with an estimated 100,000 homes waiting for service across the country on 12 January.

British Gas publicly said it was clearing 40% of the 10,000 jobs from households on strike days – but GMB says this is ‘seriously misleading’.

The union claims the normal volume of jobs from households varies between 20,000 and 25,000 daily. The ratio is approximately three breakdown jobs to one service job. Plus there is all the normal routine servicing on top of this workload.

On strike days none of the routine service work is done and only 15% of the breakdowns are dealt with. So the figure for the growth in the backlog is treble the 6,000 claimed by the company.

British Gas parent company Centrica reported an operating profit  of £901m in 2019. The operating profitability of its UK home heating business rose by 27% in the first six months of 2020.

Justin Bowden, GMB national secretary, said: “The backlog of households awaiting services for British Gas is growing at treble the 6,000 per day the company admits. The claim that they are clearing the backlog on non-strike days is also not accurate.

“The fire and rehire changes being imposed on engineers mean hourly pay rates would be 15% below agreed pay rates along with other worse term and conditions. It was wishful thinking in the extreme to think that union members would ever acquiesce with cuts of this magnitude in a profitable company.

“British Gas should accept that taking fire and rehire off the table is the only way to end this dispute.”

Centrica, British Gas’ parent company, has been approached for comment.