A £1 billion investment pot for the North-East is at risk if Britain quits the European Union, a Labour MP has warned.

Cash for “transport infrastructure, small business support, international trade support and digital skills” could be lost, Sedgefield MP Phil Wilson told ministers.

The warning came as David Cameron ducked a call from a second North-East MP - Easington’s Grahame Morris - to publish a Treasury document on the estimated costs of leaving the EU.

Instead, speaking in the Commons, the Prime Minister heaped praise on the Nissan factory, in Washington, for “producing more cars than the whole of the Italian car industry”.

Mr Cameron said: “It is a great example of the manufacturing renewal that is taking place in this country.

“I want the widest possible debate about Britain’s future in Europe and I would encourage all organisations to bring forward ideas, facts and figures so that this debate can be formed.”

But, earlier, Mr Wilson questioned how any MP in the North-East could favour EU withdrawal, when membership is so vital to the region’s prosperity.

This week, Anne-Marie Trevelyan, Conservative MP for Berwick-upon-Tweed, allied herself with 50-odd Tory MPs ready to back a British exit if Mr Cameron fails to negotiate radical reform.

And James Wharton, the Stockton South MP, has demanded big changes on employment law, working hours’ limits, criminal justice, defence and foreign policy, saying – two years ago – “How I vote depends on what's on the table at that time.”

Mr Wilson said: “Europe creates jobs and growth, it means investment in the North-East, it protects our rights, it keeps us safe and it improves the environment.

“According to the North-East Chamber of Commerce, over 63 per cent of businesses in the North-East want us to be part of Europe.

“We also gain in net terms from our contributions to Europe in respect of social and economic investment in the North-East.

“There will be £1bn of investment in the North-East over the next six years for transport infrastructure, small business support, international trade support and digital skills.”

Mr Wilson accused the Conservatives of playing “games”, adding: “This referendum issue is ultimately not about what the people think, but about whether it can keep the Conservative party together.”

And, pointing out 50 per cent of the cars made by Nissan are sold in the rest of the EU, he said: “I do not want to see the factory going to Spain, France or anywhere else.

“I want it to stay in Europe as one of the most productive car plants in the world.”

Both Nissan and Hitachi – which is building a train-assembling factory at Newton Aycliffe, County Durham – have warned future investment is at risk with EU withdrawal.