Brexit impact analysis papers outline the impact on the UK economy of several potential immigration policies after Brexit.
The documents show that even if Britain adopts a relatively flexible immigration policy leading to a smaller drop in EU migration, its negative effects would outweigh the 0.2 per cent boost to economic growth expected if a new trade deal with the US was agreed.
The study, EU Exit Analysis - Cross Whitehall Briefing, was leaked to BuzzFeed News this week. Compiled by Whitehall officials, it found that UK economic growth would be lower under all three post-Brexit scenarios modelled.
It said the combined effect of trade barriers and lower immigration could mean UK borrowing is tens of billions of pounds higher in 2033-34 than under the status quo, even when a potential US trade deal is taken into account.
Ministers on Wednesday bowed to pressure to publish the secret impact assessment just hours after Theresa May had refused to do so.
The Prime Minister had said MPs would be given the assessment of the consequences of leaving the EU before voting on the final deal. But after Labour tried to use an obscure parliamentary device to force their release, the government conceded the documents would be released sooner.
A government spokesman said: "The UK will remain an open and tolerant country; one that recognises the valuable contribution those with skills and expertise make to society while also ensuring there is control of the overall numbers of migrants that come to the UK.
"As we leave the EU, we will forge new and ambitious trade deals around the world, with trading partners old and new."
