Theresa May has dismissed the significance of leaked Government studies which indicated that any outcome from Brexit would leave Britain worse off.
The Prime Minister pledged that MPs will be given full and "appropriate" analysis papers on the likely impact of the final Brexit deal before they are asked to vote on it.
Papers prepared by the Department for Exiting the EU and obtained by website Buzzfeed suggested that even with a comprehensive trade deal of the kind May is seeking, UK growth would be down by 5% over the next 15 years.
This would rise to 8% if Britain left without a deal and was forced to fall back on World Trade Organisation rules.
Yesterday (January 30) one of May's ministers warned official assessments which predict an economic hit from Brexit cannot be dismissed.
But the Prime Minister said the findings were "very preliminary" and did not address the actual deal which she is hoping to conclude.
"It would be wrong to describe this as 'the Brexit impact assessment'," the Prime Minister told reporters travelling with her on a trade mission to China.
"What has been seen so far is a selective interpretation of a very preliminary analysis, which ministers have not signed off, have not approved, and which doesn't actually even look at the sort of deal that we want to deliver in terms of the future relationship with the European Union."
Labour is to seek to force the Government to release its latest assessment of the impact of Brexit on the economy through a binding Commons vote.
The party is to use the same archaic parliamentary procedure it adopted last year to force ministers to release Brexit impact papers to a Commons select committee.
The latest leaked study, drawn up for the Department for Exiting the EU, concluded the UK economy would lose out, whatever Brexit deal the Government struck with the EU.