“We’ve been doing all we can to develop our UK business, restore Vauxhall and Opel profitability, reinvesting in Luton and improving our sites’ competitiveness in order to help them face up to an uncertain future," Maxime Picat told Reuters at the Paris auto show.

"But there are limits. Those limits are customs barriers, and the loss of freedom of movement, for people and goods. If we get to that point, we will be obliged to take measures.

"If we suddenly have to start manufacturing for the UK in the UK, and for Europe in Europe, there will necessarily be an impact on UK production," Picat said in an interview.

"We’re not going to be dogmatic about it, and there's no question of punishing the UK. We'd take a look at our two factories, the state of our business, and look for a solution. But I don’t know where that will lead us in terms of the sustainability of our sites."

(Reporting by Laurence Frost; Editing by Mark Potter)