Toto Wolff believes Brexit will leave British-based Formula One teams at a major disadvantage – and a no-deal outcome would be a nightmare for the industry.
Mercedes chief Wolff insisted Brexit would hand Ferrari more power over his Brackley-based team.
The UK will depart the European Union on March 29 and there is currently no deal in place.
"Ferrari in Italy, Alfa Romeo in Switzerland, they would have a massive advantage over every UK-based team," said Wolff, speaking as his team put their new car through its paces at testing in Barcelona.
"We are looking at the various scenarios with Mercedes-Benz UK because it not only impacts Formula 1 but it impacts also the mother brand in terms of getting cars and parts in and out of the country.
"But I can see very much if a 'no-deal' Brexit would happen like has been discussed, I think it would have a major impact in terms of our operation going to the races and getting our cars developed and ready.
"So that is a nightmare scenario that I don't want to even envisage.
"We do have certain contingencies in place, like more stock and thinking about how we would get parts and people in and out of the country – but it would be a disruption and it would cause all the UK teams a lot of headaches.
"Brexit is a major concern for us and should be a major concern for all of us that live in the UK and operate out of the UK."
Lewis Hamilton and Mercedes are aiming to defend the drivers' and constructors' titles when the season starts in Australia next month.
Wolff also revealed Hamilton has been working out as he looks for a sixth title.
He added: "The weight regulations have been lifted and he has come back stronger and musclier than before.
"He's in a super mental state, the best I've seen so far. He looks physically and mentally in shape. Half an hour before the session he was all ready to go. I think a good start."
