At least 1,000 workers at Jaguar Land Rover’s historic Castle Bromwich factory have been told they will drop down to a three-day working week until Christmas.

The change comes as the car giant claimed it is struggling as a result of Brexit and a fall in demand for diesel models.

Jaguar Land Rover said it was making “temporary adjustments to our production schedules” at the former Spitfire factory that makes the XF, XJ and XE Jaguars as well as the F-Type sports car.

The move affects about half the Birmingham plant’s 2,000 workers, who will remain on full pay, and comes in the wake of moves in April this year to axe 1,000 agency jobs at the Solihull factory.

The company employs thousands of both full-time and agency workers at sites across the West Midlands including in Castle Bromwich, Wolverhampton, its head office in Coventry and Solihull.

Jaguar Land Rover has been making plans over the past few years to target the hybrid and electric markets and said last year that from 2020 all new Jaguar Land Rover vehicles would be electrified.

Earlier this year, JLR said it would temporarily reduce production at its plant in Halewood, Merseyside, in response to weakening demand due to Brexit and tax hikes on diesel cars.

And just a week ago Jaguar Land Rover boss Ralf Speth blamed the cutbacks on the fact that diesels had been “demonised”, leading to a potential £1.2bn annual cost to the company. He also warned that a hard Brexit would could cost tens of thousands of jobs at JLR and its supplier companies in the UK.

On Monday, Tory MP and Brexit supporter Sir Bernard Jenkin claimed Spelth was “making it up”.

“We’ve had figures made up all the time by the scaremongers in this debate and I’m afraid nobody believes them,” he told BBC Radio 4′s Today programme.

But Birmingham MP Jack Dromey hit back on Twitter, saying: “This morning, a wide-eyed Brexiteer Bernard Jenkin MP, in his ideological zeal, accused Jaguar Land Rover chief executive Ralf Speth of ‘making it up’.

“Now we know fears are justified. A hard Brexit or no deal will be catastrophic for Britain’s automotive industry.”

JLR said in a statement: “As is standard business practice, Jaguar Land Rover regularly reviews its production schedules to ensure market demand is balanced globally.

“In light of the continuing headwinds impacting the car industry, we are making some temporary adjustments to our production schedules at Castle Bromwich.

“We are however continuing to over-proportionally invest in new products and technologies, and are committed to our UK plants in which we have invested more than £4bn since 2010 to future proof manufacturing technologies to deliver new models.”