The boss of Nissan Carlos Ghosn has admitted that the car giant's UK investments will be "re-evaluated" if Theresa May delivers a bad Brexit deal, despite last October's high-profile commitment by the firm to build its next Qashqai and X-Trail model at its Sunderland plant.

Nissan's decision - which followed mysterious assurances from the Government about the firm's future terms of trade with Europe - was hailed as a much-needed vote of confidence in post-Brexit vote Britain and a welcome guarantee of thousands of jobs in the North East.

But speaking to reporters at the World Economic Forum in Davos today Mr Ghosn made it clear that the French firm's commitment was still conditional and that if the shape of the final Brexit deal is detrimental to Nissan's competitiveness it could yet pull out of UK operations.

"Obviously when the package comes, you are going to have to re-evaluate the situation, and say, okay, is the competitiveness of your plant preserved or not," he said.

However, according to Reuters, Mr Ghosn stressed he assumed the Government would ensure Sunderland remained competitive.

"We're going to have to make decisions on investment within the next two to three years. So obviously the faster the Brexit results come, the better," he said.

The surprise October announcement by Nissan was hailed by Brexiteers as evidence that the negative impact of Brexit on UK car makers, which heavily export to the Continent, was over-exaggerated.

Earlier this week Theresa May said that the UK planned to leave the single market and that it would aim to conclude a free trade deal with the rest of the European Union.

If the UK fell back on basic World Trade Organisation rules UK car exports to Europe would attract tariffs of 10 per cent.

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Another fear for car makers is the prospect of Britain leaving the EU customs union, which would entail costly "rule of origin" checks at customs.

This is a particular danger for car firms since their supply chains tend to be integrated across the EU, meaning they import and export various components across borders several times.

In her speech Ms May floated the prospect of a compromise to preserve some elements of the customs union with the EU for the UK for specific sectors, although the legality and practicality of such an arrangement is unclear.

Nissan's October pledge followed a meeting between Mr Ghosn and Ms May. Nissan had previously threatened to pull out of Sunderland, where 7,000 people are employed, unless the Government guaranteed compensation for costs relating to any new tariffs resulting from Brexit.

Nissan said that the Government had made a "commitment" that the plant's competitiveness will not be damaged.