The UK government's own analysis of the impact of leaving the European Union shows Britian would be worse off outside the economic bloc under every scenario it has modelled.
In a January 2018-dated paper seen by BuzzFeed News entitled "EU Exit Analysis - Cross Whitehall Briefing", three of the most plausible exit scenarios are mapped out in detail by Whitehall officials.
The paper summarises that almost every sector and every region of the UK would be negatively affected under each Brexit scenario.
Under the scenario where Britain is left without a deal and forced to comply with World Trade Organisation rules, the briefing suggests that economic growth would see a negative impact of 8% over the next 15 years.
Free trade agreement
If the UK were able to negotiate a fully-functioning free trade agreement with the EU, which the prime minister and her negotiating team are aiming for, the negative impact would still be 5%, the paper says.
Meanwhile, if the UK retains access to the single market through membership of the European Economic Area, the hit to growth over the next 15 years would move down to just 2%.
The government issued a statement over the leaked document saying it contained a number of important caveats and that the headline findings should not be interpreted without considering these caveats.
"As part of its preparations for leaving the European Union, officials from across Whitehall are undertaking a wide range of ongoing analysis," the statement said.
"[The paper] is hugely dependent 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."
Other warnings from the paper included the erosion of London's position as a major financial centre.