FORMER Prime Minister Tony Blair said Nissan must have been given "very strong assurances" by the Government on access to the single market before boosting its UK car production.

Mr Blair, former MP for Sedgefield, County Durham, said he backs moves by the Government to keep investment in the UK.

But he said: "I know the leadership at Nissan.

"I'm absolutely sure they would not have made this commitment unless they received very strong assurances from the UK Government." He told BBC Radio Four's Today programme: "Now, if the UK Government are giving those assurances, I welcome that.

"I should imagine they gave strong assurances about the car industry's access to the single market. If this is an indication that the UK Government are giving strong assurances about access to the single market, this would be important."

The Japanese giant's decision to build its next-generation Qashqai, and add production of the new X-Trail model, at its Sunderland plant was seized on by Prime Minister Theresa May as proof that the UK was an attractive investment hub despite the flux caused by the Brexit vote.

But Ministers have side-stepped reports Nissan was given written guarantees it would be compensated if the EU imposed a post-Brexit tariff barrier against British exports.

Hartlepool MP and Labour chairman of the Commons Business Committee, Iain Wright, insisted Business Secretary Greg Clark must appear before the watchdog to give evidence on the matter.

Mr Wright told the BBC: "On the one hand, it's taxpayers' money, and, I think, we would need to know. And, on the other, it could be commercial confidence as well.

"But, in terms of transparency, in respect of how government will intervene and provide that reassurance and support, I do think that's important."

Former business secretary Sir Vince Cable said, if there was no compensation or mitigation offered, it must mean the UK is remaining in the EU customs union as Nissan would not go ahead without "copper-bottomed promises".

Sir Vince told The Guardian: "I was involved in discussions with Nissan in their last big round of investment decisions. Even under the coalition they were toying with doing it in France.

"I find it impossible to believe they would go ahead without some pretty copper-bottomed promises. These guys do not go making decisions on the basis of vague assurances. That is not the way they operate."

And former business minster Anna Soubry, who held initial post-Brexit discussions with Nissan while in government, said she would be "very surprised" if there was no guarantee to mitigate tariffs.

She said David Cameron's government was "very seriously" looking at compensation for any duties imposed on the automotive industry once Britain left the EU.

The Remain-backing Tory MP said she met Nissan on June 30, a week after the Brexit vote, and that the company expressed "profound concerns" about tariffs.