Brexiteer backbenchers and ex-ministers branded them “deeply worrying” and accused the prime minister of having abandoned her “red lines”.
They were responding to the white paper setting out details of Ms May’s plans for a future relationship with the European Union.
The document’s viability was immediately challenged when an alternative version, penned by ex-Brexit secretary David Davis, was published online.
The EU itself gave the white paper a muted welcome, while US president Donald Trump, arriving in the UK on Thursday, breached diplomatic protocol to suggest that Ms May’s plans were not what the British public voted for.
After the government published the document, The Future Relationship Between the United Kingdom and the European Union, new Brexit secretary Dominic Raab found himself defending it in the commons.
As well as the usual fire from the Labour benches, he faced a torrent of difficult questions from Tories, including ex-ministers, among which was one who had quit Mr Raab’s department days earlier in a row over Ms May’s proposals. Jacob Rees-Mogg, who chairs the pro-Brexit European Research Group of Tory MPs, said the package amounted to “vassalage” for the UK.
Mr Rees-Mogg went on: “There are very few signs of the prime minister’s famous red lines.
“It is a pale imitation of the paper prepared by David Davis, a bad deal for Britain. It is not something I would vote for nor is it what the British people voted for.”
Former Tory leader Iain Duncan Smith told ministers he had “deep misgivings” about the white paper, adding: “I voted to leave, not to half-leave.”
Eurosceptic Tories claim the 98-page document, which prompted the resignation of Boris Johnson and Mr Davis earlier this week, sets out a significantly “softer” version of Brexit than the 2016 referendum mandated for.
Ms May’s plans entail an “association agreement” – first reported by The Independent three weeks ago – involving the UK accepting a “common rulebook” on trade in goods, and a commitment to ongoing harmonisation with EU regulation.
Brexiteers argued this was tantamount to staying in a single market, stymieing the UK’s ability to conduct trade deals elsewhere – something ministers denied, claiming instead that it would help frictionless trade with the EU.
Under the proposals, the UK would also make continued payments to the EU for participation in shared agencies and programmes.
An independent arbitration panel set up to resolve UK-EU disputes, would be able to seek guidance from the European Court of Justice on the interpretation of EU law.
But Brexiteers claimed the loose wording of the document pointed to the UK remaining under the ECJ’s jurisdiction
There would be new arrangements for services, giving each side the freedom to set its own rules and meaning potentially less access for the UK into the EU’s markets in these sectors.
On immigration, the plans mooted new “mobility” rules which could see deals on visas done as part of a trade negotiation and visa-free travel for tourism and temporary work.
During the debate, Brexiteer Sir Bill Cash, who chairs the Commons European Scrutiny Committee, complained that a “common rulebook” with the EU would see the UK becoming a “rule-taker” from Brussels.
Conservative former cabinet minister Theresa Villiers said a promised right for parliament to reject future EU rules, would mean nothing because “the white paper commits to an upfront choice to commit by treaty to ongoing harmonisation.”
Mr Raab responded saying there would be a “parliamentary lock” and “proper democratic oversight” of any future EU regulations translating into UK law.
Former Brexit minister Steve Baker, who resigned over the proposals earlier this week, questioned whether the proposals were achievable.
Extracts of Mr Davis’s alternative white paper, published on the ConservativeHome website, showed that the former Brexit secretary was planning a looser free trade arrangement with the EU before he left office.
Others questioned the migration plans, with Mr Duncan Smith suggesting the government was using people’s right to come to the UK as “negotiating capital”.
He said: “My simple question is, when the government goes to discuss, negotiate or confer with the EU, whichever phrase suits, does he believe that they will be prepared to withdraw the rights to benefits for those who come without jobs?”
Conservative MP Sir Edward Leigh demanded an assurance that “any preferential treatment given to EU migrants will not be part of a withdrawal agreement, but will be entirely in the hands of this parliament post-Brexit.”
Brexit negotiator Michel Barnier said only that he would assess the white paper’s contents to see if they were “workable and realistic” ahead of negotiations with Mr Raab next week.