NISSAN could slash investment in its flagship North-East car factory if Britain leaves the European Union, Nick Clegg revealed last night.

The deputy prime minister said the Japanese car giant had already warned that it would review its investment plans if Britain walks away from Europe.

And he revealed Nissan executives had said Britain’s membership of the EU was a key factor in its decision to build the all-electric Leaf hatchback in Sunderland.

Nissan and its French partner Renault have several other manufacturing sites in Europe but Sunderland is the most productive plant in the EU.

Ministers hailed Nissan’s decision to build the Leaf in the UK as hugely significant. As well as the new car, Nissan also gave the go-ahead to build a battery plant alongside the factory despite intense lobbying from European politicians keen to see it built abroad.

The £420m project – launched in March - will create 560 jobs at the plant and a further 1,500 at supply companies across the North-East.

Nissan Sunderland already builds more car than the whole of Italy and several important new models, including a replacement for the best-selling Qashqai, are penciled in over the next couple of years.

Sunderland has also been chosen to build a new small hatchback for the group’s premium marque, Infiniti.

Speaking in Westminster, Mr Clegg pointed to Nissan’s decision to build “low emission cars” in Sunderland as evidence of the firm’s “faith in the North-East”.

But he added: “By the way, they are also saying they wouldn’t have done so if they felt the United Kingdom would be leaving the European Union.

“That shows the North-East has great deal to offer, as the North-East of England, but also as a region remaining firmly rooted within the European Union.”

The comments are unusual because major companies are reluctant to speak publicly about the highly-political issue of the EU referendum – promised by David Cameron, for 2017.

However, Nissan’s warning is not without precedent. In 2004, the company’s chief executive, Carlos Ghosn, warned that he would not commit new models to the Sunderland factory without reassurances that the UK was moving towards joining the single currency.

However, the company later retracted the warning after finding a way to “work around” the single currency issue.

Earlier this year, it was reported that the president of Hitachi said it would be a disaster for investment if Britain withdrew from the EU.

However, the company has made no public comment about the likely impact on its train-assembly factory to be built at Newton Aycliffe, County Durham, creating 730 jobs.

Asked when it had told Mr Clegg that leaving the EU would hurt investment in Sunderland, Nissan replied: “We don’t have any comment to make on this.”

An aide to the Liberal Democrat leader acknowledged that Nissan had made no public statement about its intentions.

But he added: “The point Nick was making was about the huge damage leaving the EU would have on our attractiveness to Japanese car manufacturers.”

In January, the Prime Minister pledged an “in-out” EU referendum, if he wins the next general election, following negotiations on a new settlement with Brussels.

Phil Wilson, the Sedgefield MP, whose constituency includes the Hitachi site, said: “This is one occasion when I agree with Nick.

“I think he has let slip the very real concerns of people in our industries about the impact on jobs of coming out of the EU.”