The government is due to publish its economic analysis on the long-term effects of Brexit on the UK.
Various scenarios will be set out by the Treasury – with the Daily Telegraph saying it will predict £150bn in lost output over 15 years under no deal, with Theresa May’s plan costing £40bn.
Meanwhile, the PM will visit Scotland and argue she was “robust” in defending UK fishing in her Brexit talks.
The SNP claims the the industry will be “sold out”.
The party says access to UK waters for EU boats will be used as a “bargaining chip” to secure a good post-Brexit trade deal.
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However, Mrs May will continue to maintain the Brexit withdrawal agreement she has agreed with the EU secures the UK “full sovereign control over our waters” and is the best way to protect the economy.
According to the the Daily Telegraph, the Treasury analysis will show that under Mrs May deal, the UK’s GDP will be between 1% and 2% lower over 15 years than if it stayed in the EU, compared with 7.5% lower under a no deal situation.
The Department for Exiting the EU said it does not comment on leaks.
The Telegraph also quotes the former Brexit Secretary Dominic Raab saying the Treasury’s analysis “looks like a rehash of Project Fear”.
In other developments, the Commons Public Accounts Committee issued a report warning of a “real prospect” of “major disruption” at UK ports in the case of a no-deal Brexit.
MPs are due to vote on Mrs May’s Brexit deal, which she insists is the only option, on 11 December.
Against this backdrop, the prime minister is visiting different parts of the UK to engage directly with the public and businesses in a bid to build support for the deal.
She insisted it protected the “vital interests” of the whole of the UK when visiting Wales and Northern Ireland on Tuesday, while denying claims from DUP leader Arlene Foster that she had “given up” on negotiations before agreeing the Brexit deal.
During a visit near Glasgow, Mrs May will speak to factory workers about how she believes her deal provides an “unprecedented economic relationship that no other major economy has” and certainty for employers and their staff.
“We will be free to strike our own trade deals around the world, providing even greater opportunity to Scottish exporters,” she will say.
She will also say that moving away from the EU’s common fisheries policy (CFP) “which has so tragically failed Scotland’s coastal communities” will leave the UK “free to decide for ourselves who we allow to fish in our waters”.
The UK sells nearly £1bn of fish produce to the EU every year, and a number of EU countries are insisting that tariff-free trade of that kind can continue only if EU fishing boats continue to get access to UK waters.
Scottish Conservative Ross Thomson, has already voiced concerns the draft deal could lead to the “continuation of some form of the CFP”.
And Scottish First Minister Nicola Sturgeon has unveiled analysis the SNP claims shows Scotland would be left poorer by the deal.
Her party, which has 35 MPs, along with the leadership of Labour, the Lib Dems and Democratic Unionists have all said they will reject Mrs May’s deal.
Many Tories have also said publicly they are opposed to Mrs May’s deal.
Legal advice row
Meanwhile, a row is brewing after the Labour party demanded the government publish its full legal advice on the Brexit deal this week.
The government has only said it will publish a “full reasoned position statement” laying its out political and legal position on the withdrawal agreement.
BBC Newsnight political editor Nick Watt said a source says the full advice provides a “very stark warning” that there is no way the UK, on its own, would be able to get out of the so-called Northern Ireland backstop.
The backstop – the plan to create a temporary single customs territory to prevent the return of customs posts at the Irish border in the event no EU-UK trade deal comes into force – is controversial because Brexiteers fear it would keep the UK tied to EU rules indefinitely.