The next generation of the Vauxhall Astra will be built in the UK, but it will be conditional on the final terms of the UK's exit from the European Union, the car giant has announced.
Parent group PSA said the new model will be built in Ellesmere Port on Merseyside, which employs over 1,000 workers, if a satisfactory Brexit deal is reached.
The PSA Group said it will also invest in the Russelsheim plant in Germany to manufacture Opel Astras from 2021.
A company statement said: "Since the acquisition of Vauxhall Motors by Groupe PSA, we have been working hard to turn around the fortunes of the brand and to address the performance of the commercial and manufacturing divisions.
"Currently, the Vauxhall and Opel Astra are built in Ellesmere Port and in Gliwice, and our bestseller is still in the middle of its life cycle.
"Groupe PSA has today announced its intention to manufacture the next generation Astra in two plants in Europe.
"The group has confirmed that the Russelsheim plant will manufacture Astra and that it is planned that the second plant will be Ellesmere Port in the United Kingdom.
"The decision on the allocation to the Ellesmere Port plant will be conditional on the final terms of the UK's exit from the European Union and the acceptance of the new vehicle agreement, which has been negotiated with the Unite trade union.
"This news demonstrates the continuous effort and commitment of Groupe PSA to Vauxhall Motors."
Car production has been falling in the UK over the past year, amid increasing pleas from the industry for a Brexit deal.
The UK's automotive industry has received a series of blows in recent months, with Honda announcing it will close its Swindon plant in 2021, and Ford saying its Bridgend engine plant in south Wales will close in September 2020 with the loss of 1,700 jobs.
Unite regional officer Mick Chalmers said: "Unite has been in positive discussions with PSA about a new vehicle agreement and securing new models for Vauxhall's Ellesmere Port plant.
"A no-deal Brexit will destroy all of that along with the hope of securing the plant's long-term future.
"It is imperative for the future of the thousands of people who depend on Vauxhall Ellesmere Port that a no-deal Brexit is taken off the table and a deal reached with the European Union that secures frictionless trade and tariff free access.
"This will then allow PSA to commit to allocate the new Astra to Ellesmere Port and for Unite to put the new vehicle agreement to our members for ratification."
The union's assistant general secretary Steve Turner added: "A no-deal Brexit would be catastrophic for people working in car factories and workers in the supply chain.
"The no-deal Brexit virility test of the Tory leadership contenders needs to stop.
"Boris Johnson and Jeremy Hunt need to wake up to the harm that a no-deal Brexit will have on people's livelihoods and futures.
"They need to take no-deal off the table and commit to securing a customs union with the European Union which guarantees the frictionless trade and tariff free access that is central to the success of the UK car industry and wider manufacturing."