A regional breakdown of the analysis emerged on Wednesday as Theresa May chaired the first of two key Brexit meetings with senior ministers as the government faces more calls to clarify the UK's position.
Mrs May vowed to be "robust" in Brexit talks after Brussels released papers showing it wants to put in place a method to rapidly curtail the UK's single market benefits if it breaches agreements on a transition deal.
"As the poorest English region, the North East was inevitably going to be more vulnerable to the economic shock of leaving the EU".
Leaks from the documents indicate leaving the European Union without a trade deal would cut Scottish economic growth by 9%.
"As ministers clearly set out in the House of Commons, this is provisional internal analysis, part of a broad ongoing programme of analysis, and further work is in progress".
A no-deal Brexit scenario would result in Scotland suffering a 9% hit to its GDP, according to the UK Government's own leaked analysis.
As it stands, however, the United Kingdom is expected by Brussels to sign off on the text which will see Northern Ireland remain under European Union law at the end of the 21-month transition period, wherever it is relevant to the north-south economy, and the requirements of the Good Friday agreement.
Mrs May yesterday chaired the first session of her Brexit "war Cabinet" created to win support for negotiating strategy.
The uncompromising legal language of the draft agreement is likely to provoke a major row, something all parties to the negotiations have been trying to avoid.
Earlier this week, George Hamilton, chief constable of the Police Service of Northern Ireland, warned that any infrastructure at the border, however light, would become a target for armed groups and pose a danger to his officers. Whitehall calculated that the UK's growth would be down by eight per cent over 15 years under this scenario.
In the West Midlands there could be a 13% decline in GDP, while Northern Ireland could suffer a 12% fall.
"Members of all parties should be uniting in the national interest to present the resounding case for Wales to remain in the single market and customs union", he said.
Jude Kirton-Darling, Labour MEP for the North East of England, added: "As disquieting as this may be, it is unfortunately only the beginning of a string of terrible news to come out of the leaked impact assessment papers, and the direct result of the Tories being incapable of negotiating a Brexit deal that won't drain all money and economic prospects out of the North East". It said chemicals, clothing, aviation, cars and retail would be particularly hard hit.