Tata Motors-owned Jaguar Land Rover joined other major businesses in the UK in offering a stark message on the need for certainty, as it warned that a bad Brexit deal could cost the company more than £1.2 billion profit each year, putting £80 billion of further investment and jobs at risk.

“If the UK automotive industry is to remain globally competitive and protect 300,000 jobs in Jaguar Land Rover and our supply chain, we must retain tariff and customs-free access to trade and talent with no change to current EU regulations,” said CEO Ralf Speth late on Wednesday, as he warned that he and his supply chain partners faced an “unpredictable future” if Brexit negotiations did not maintain “free and frictionless trade” with the EU and unrestricted access to the single market.

A “bad Brexit deal” would force the company to “drastically adjust” its spending profile, which had resulted in £50 billion in investment in the past five years, and plans for a further £80 billion in the next five. “This would be in jeopardy should we be faced with the wrong outcome.”

The warning came ahead of a cabinet summit on Brexit at Chequers, the Prime Minister’s country retreat, at which Theresa May will attempt to rally support for her plans for a final Brexit deal ahead of a meeting with EU leaders. The message was seized on by those concerned about the direction of Brexit negotiations.

“For people in manufacturing towns and cities, this is not a joke or an idle threat. We are talking about the loss of hundreds of thousands of jobs with a devastating impact for our economy,” said Alison McGovern MP, who supports the “People’s Vote” campaign for a second referendum on the final Brexit deal.

Len McCluskey, general secretary of the UK’s biggest union Unite, called on the government to stop playing “Russian roulette” with people’s jobs and livelihoods. “Drop your redlines and secure a decent deal, one that is to the benefit of the working people of this country.”

On Thursday the government sought to offer assurance to the company. “JLR is a great British success story. We are determined to make sure that it can continue to prosper and invest in Britain,” said Britain’s Business, Energy and Industrial Strategy Minister Greg Clark, considered one of the cabinet members pushing for a softer Brexit.

From cautionary messages in the immediate aftermath of the referendum, global businesses in the UK have grown increasing vocal and frank in their assessment of what Brexit, in the current form being pursued by the government, would mean for them. Airbus and BMW are among those to have warned their presence in the UK was at risk.

In recent months JLR has announced the shifting of production of its Land Rover Discovery to a plant in Slovakia and 1,000 job losses.

UK new car sales are down 6.3 per cent so far this year, according to data released on Thursday by motoring organisation the SMMT, which called for a “technology neutral strategy” from government – including support for new-tech diesel vehicles, amid uncertainty within the market.