BRUSSELS (Reuters) - The EU executive has asked the British government for details of assurances it gave to Japanese carmaker Nissan <7201.T> that new investment would not suffer when Britain leaves the bloc, a European Commission spokesman said on Monday.

"We have seen the press reports regarding Nissan and as a result the Commission ... is in contact with the UK authorities," the spokesman told reporters when asked if the executive was checking whether such assurances might breach rules in the EU against states giving unfair aid to companies.

"The UK authorities have not notified any support to Nissan for assessment under our state aid rules and we've therefore not taken any formal view of this matter," the spokesman added.

Asked to clarify what prompted the questions to London, he replied: "We follow events, we read press reports ... If we see something interesting then we ask questions."

Depending on the terms of its exit from the EU following its referendum vote in June, Britain may well no longer be bound by EU state aid rules following Brexit. But as long as it remains a member, it would not be able to favor particular companies.

The British government said last month that it have given Nissan assurances that its new investment in plant in Britain would remain competitive after Brexit but said the firm had not been given any explicit promise of compensation for EU tariffs.

(Reporting by Alastair Macdonald; editing by Philip Blenkinsop)