The Government has been accused of playing "Russian roulette" with tens of thousands of jobs following a warning from car giant Jaguar Land Rover over the impact of a hard Brexit.
The company said it urgently needs "greater certainty" on Brexit to continue to invest heavily in the UK and safeguard suppliers, customers and 40,000 British-based jobs.
The warning from the country's biggest car maker follows similar statements from BMW and Airbus and comes ahead of a crucial meeting of the Cabinet on Friday to finalise a white paper on Brexit.
Len McCluskey, general secretary of Unite, said: "Tens of thousands of decent jobs - the sort we will need more than ever outwith the EU - are being put at risk by a Government that places its survival, indulging narrow, extremist views, above the well-being of the people of this country. This is simply not acceptable.
"So I say this to the Tory party, our jobs are not yours to play Russian roulette with. Drop your red lines and secure a decent deal, one that is to the benefit of the working people of this country.
"And if you cannot agree to put people before your ideology then move over and let a party that will get on with it."
Dr Ralf Speth, chief executive of JLR, said the company's "heart and soul" is in the UK.
"However, we and our partners in the supply chain face an unpredictable future if the Brexit negotiations do not maintain free and frictionless trade with the EU and unrestricted access to the single market.
"We urgently need greater certainty to continue to invest heavily in the UK and safeguard our suppliers, customers and 40,000 British-based employees.
"A bad Brexit deal would cost Jaguar Land Rover more than £1.2 billion profit each year."
Mr McCluskey said he also had a message for employers of Unite members: "If you think that a Tory Brexit is a green light for the dash to the door, or to diminish pay and living standards, then think again.
"We will never allow our members to suffer because your profits are being put before our people.
"Business, if you care about decent jobs and a stable future for generations to come then do not allow these Tory Brexit nightmares to come true."
Shadow business secretary Rebecca Long Bailey said: "This stark warning from one of the jewels in the crown of British automotive manufacturing should be a klaxon call to Theresa May and her Cabinet.”