A Government minister refused six times to say what post-Brexit financial help Nissan has been promised to build its new cars at its flagship Sunderland plant.

Greg Clark came under fierce pressure to reveal any deal struck with the Japanese carmaker after it threatened to invest abroad instead – putting hundreds of jobs in England’s poorest region at risk.

Ministers were elated after Nissan announced it will after all build its next-generation Qashqai in Sunderland, as well as add production of the new X-Trail SUV model.

Theresa May hailed it as "fantastic news”, adding: “This vote of confidence shows Britain is open for business and that we remain an outward-looking, world-leading nation.”

The agreement was a triumph for Mr Clark, the Business Secretary, who flew to Japan last week to give assurances to Nissan’s executive committee.

Similar assurances – believed to be that the company will not face worse trading conditions following Brexit – were first given by the Prime Minister to Nissan chief Carlos Ghosn two weeks ago.

There is speculation that Nissan was promised compensation for any future tariffs it might face if, as expected, Britain leaves the single market, or exemptions from trade barriers.

Crucially, other car companies operating in the UK, such as Toyota, Honda and Vauxhall, are likely to expect to be offered the same terms as Nissan when they make their investment decisions.

Any such help could eventually run up a huge bill for the Government, as carmakers face 10 per cent tariffs if Britain ends up working under World Trade Organisation (WTO) rules.

On the BBC’s World at One, Mr Clark was asked six times whether the Government had struck a deal with Nissan, but refused to give a clear answer.

At one point, Mr Clark said: “I think we do have mutual confidence that this is going to be a very exciting place to invest and that’s what we agreed.”

Colin Lawther, Nissan's senior vice president in Europe, denied the Government had offered specific compensation to the company, saying: “There's nothing, there's no special deal for Nissan.”

But he hinted at help for the entire car industry, adding: “We are working within the whole of the automotive industry. We would expect nothing for us that the rest of the industry wouldn't be able to have access to.”

Jeremy Corbyn led demands for the details of any deal between the Government and Nissan to be revealed.

The Labour leader said: “It must be made public, because it is public money that will be used if there are any inducements that have been offered and quite obviously, if you are offering big inducements to one industry or one manufacturer, then all the others will quite reasonably say, ‘Well, what about us?’”

Later, Downing Street insisted there was no “special deal” either for Nissan or the wider automotive industry in the UK.

A No 10 spokesman said: “There is no compensation package. What was made clear to Nissan and to others in the automotive industry is that what we want is a competitive environment for the whole of the industry.”