The West Midlands and the North East of England will be hurt the most by Brexit , the Government's leaked analysis has revealed.

And Prime Minister Theresa May faced demands to publish the papers in full.

A new government analysis of the impact of Brexit, leaked to website Buzzfeed after it was supposed to be kept secret, shows that the UK would be worse off outside the European Union under every scenario modelled.

And it shows that every UK region would be affected negatively in all the modelled scenarios, with the North East and the West Midlands facing the biggest falls in economic performance alongside Northern Ireland.

But the papers, prepared by officials across Whitehall for the Department for Exiting the European Union, are still being kept secret. All that's been revealed is what was published on the Buzzfeed website.

Birmingham MP Liam Byrne (Lab Hodge Hill) demanded that Mrs May now order the analysis be published in full.

He said: "A bad Brexit will destroy the West Midlands manufacturing industries, and it seems the Government knows it.

"It is absolutely essential that these papers are released now, so that we know what we are walking in to."

Liam Byrne MP
Liam Byrne MP

The Government analysis shows that even if the UK is able to negotiate a comprehensive free trade agreement - as Theresa May hopes - economic growth will be down an estimated 5% over the next 15 years.

That would rise to 8% if Britain left without a deal and was forced to fall back on World Trade Organisation (WTO) rules.

Alternatively, if the UK were to retain access to the single market through membership of the European Economic Area the loss would be just 2%.

The analysis, called “EU Exit Analysis – Cross Whitehall Briefing”, is being presented privately to Government ministers in one-to-one meetings this week, ahead of discussion at the Brexit cabinet subcommittee next week.

Until more details are published it won't be clear why officials believe the West Midlands and North East are likely to be hardest hit. However, both regions have large manufacturing sectors and a lot of exporting businesses.

The West Midlands is home to major car manufacturers such as Jaguar Land Rover, while the North East has a major Nissan car plant in Sunderland.

Jaguar Land Rover
Jaguar Land Rover

In response to the leak a Government source said officials from across Whitehall were undertaking "a wide range of ongoing analysis".

"An early draft of this next stage of analysis has looked at different off-the-shelf arrangements that currently exist as well as other external estimates," the source said.

"It does not, however, set out or measure the details of our desired outcome - a new deep and special partnership with the EU - or predict the conclusions of the negotiations.

"It also contains a significant number of caveats and is hugely dependant on a wide range of assumptions which demonstrate that significantly more work needs to be carried out to make use of this analysis and draw out conclusions."