Britain is so unprepared for Brexit that Theresa May should consider postponing the UK’s leaving date, an influential committee of MPs is expected to declare.

In a move that has infuriated Tory MPs, the Commons Brexit Select Committee is set to recommend that the PM should request an extension to the EU’s Article 50 process beyond next March, HuffPost UK has been told.

The idea of delaying the process beyond the official withdrawal date of March 29, 2019, is seen as so inflammatory that Conservative members of the Committee have refused to sign off the proposal and have tabled their own minority report instead.

But after a two-day drafting session, the majority of the committee have backed keeping open the option of a short, time-limited extension to Article 50 to help May get a better deal.

Their report explicitly excludes making the extension “indefinite” in any way, in order to head off claims that the MPs want to countermand the EU referendum result.

The Select Committee’s highly confidential report, due to be published on Sunday morning, has bitterly divided its members, some insiders claim.

In approving the final report, seven pro-Leave Tories and DUP MP Sammy Wilson were outvoted by their 11 colleagues, including Labour, Tory, SNP, Lib Dem and Plaid Cymru members, sources said.

Multiple amendments to the report have been proposed by the Brexiteers on the committee, a reflection of just how much they disagree with many of its findings, which they view as ‘scathing’ of the Government’s approach so far.

Among the senior Brexiteers on the committee are Jacob Rees-Mogg, who chairs the European Reform Group (ERG) of backbench Tory MPs and former Cabinet minister John Whittingdale. 

But other Conservatives decided to back committee chairman Hilary Benn in what they viewed as a measured set of proposals.

Divisions in Select Committees are not unprecedented, but it is rare that they are so deep that as minority report is published alongside a main report.

The idea of applying for an extension to Article 50, which would have to be approved by the 27 other members of the EU, has long been proposed by former Remain campaigners.

But Leavers believe it would undermine the wishes of the public, who voted by 52% to 48% in the 2016 referendum to quit the EU.

HuffPost understands that Rees-Mogg pushed the minority report move after consulting the Parliamentary ‘Bible’, Erskine May, to check that the alternative verdict had to be put on the official record in the minutes of the new report.

But one member of the committee told HuffPost that Rees-Mogg’s alternative report was tabled before there had been any discussion of amendments and Benn thought his conduct was a gross ‘discourtesy’ to the rest of the committee.

“The ERG was always going to put forward their own version,” one source said.

The Prime Minister has repeatedly insisted that she will not be requesting any extension to Article 50, the two-year negotiation process that is triggered once a member of the EU decides it wants to leave. 

Article 50’s author, former British and European diplomat Lord Kerr, called earlier this year for its deadline to be extended to allow a second referendum on the final deal that May hammers out with Brussels later this autumn.

He has told peers that “saddling yourselves with deadlines” is “crazy”, and others have argued that post-Brexit trade, customs and border changes are so complex that it will be impossible to get even an outline deal before next March.

The Brexit Select Committee published a bleak Whitehall assessment of the economic impact of Brexit last week, revealing that growth would be hit under all scenarios modelled.

Under the worst case scenario of a WTO-type ‘no deal’ outcome, GDP could drop by a cumulative 7.7% over 15 years, the analysis found. The best case scenario was a Norway-style European Economic Area deal, with GDP falling by 1.6%.

However, Government ministers and Downing Street have insisted that the analysis is flawed because it does not model the ‘bespoke’ deal that Theresa May is determined to achieve with Brussels for UK trade.

Reacting to HuffPost’s report, James McGrory, Executive Director of Open Britain, said: “When MPs from different parties join together to make it clear that the Brexit negotiations are in such a mess, and that an extension of negotiation is probably going to be required, the Prime Minister should sit up and take notice.”

Eloise Todd, CEO of the Best for Britain pro-EU campaign group said: “Britain is unprepared for Brexit. Some of this is down to the astonishing incompetence of May’s government.

“But a lot of it is because a ‘good’ Brexit just isn’t possible. Brexit, by definition, jeopardises the operations of businesses up and down the country.  Let’s be frank: instead of just delaying, it’s about time MPs fought for the right of the public to have a vote on the Brexit terms.”