The boss of Jaguar Land Rover has warned Theresa May that a “hard Brexit”  will cost the car maker tens of thousands of jobs as it will wipe out his company’s profits.

Addressing the UK’s first Zero Emission Vehicle Summit in Birmingham directly ahead of the Prime Minister, Professor Dr Ralf Speth described the prospect of a cliff-edge break with the EU as “horrifying”.

He said that if the “wrong decisions” were taken in the negotiations with Brussels, it could result in the “worst of times” for the UK, while the cost to Jaguar Land Rover would be more than £1.2bn a year.

His stark intervention follows similar warnings from other industry bosses, including Airbus and BMW, about the potentially damaging consequences of Britain’s decision to leave the EU.

Dr Speth told delegates: “If we make the right decisions this could be the best of times. If we make the wrong ones, they could be the worst of times.

“We are absolutely firmly committed to the UK, it’s our home. But a hard Brexit will cost Jaguar Land Rover more than £1.2bn a year – it’s horrifying, wiping our profit, destroying investment in the autonomous, zero-emissions, we want to share.”

He added that the loss of jobs would be “counted into tens of thousands if we do not get the right Brexit deal”.

His warning came as May pledged a £106m funding boost for research and development in zero-emissions vehicles.

The PM said it was her ambition to make Britain a leader in the green technology field, while making traffic pollution “a thing of the past”.

She said it was part of the government’s drive to build “a global, outward-facing country outside of the European Union” while investing in Britain for the long term.

“I want to see Britain, once again, leading from the front and working with industries and countries around the world to spearhead change,” she said.

“That is why I have set this country an ambitious mission. To put the UK at the forefront of the design and manufacturing of zero-emission vehicles and for all new cars and vans to be effectively zero emission by 2040.

“We have long lived with the idea that traffic is polluting. We know that no longer needs to be true. And we are on the brink of making it a thing of the past.”

May also used the event to hold roundtable talks on driving more foreign direct investment into the UK.

She was also having discussions with leading supply-chain companies from Germany, the USA, Japan, China, Spain and India.