From the moment that Geoffrey Cox, the attorney general, published his advice that, despite the prime minister’s efforts to secure an amendment to the backstop, “the legal risk remains unchanged”, the fate of the withdrawal agreement was sealed. To some, that may be taken as a signal of a deeply divided Conservative party. Yet in its commitment to honour its manifesto promise to deliver Brexit by leaving the single market, the customs union and the remit of the European court of justice, the party is anything but.

My own local association voted unanimously last month that Brexit, as defined in the manifesto, must be delivered on time and in full. The National Conservative Convention – the senior body in the voluntary party – passed a similar motion by a ratio of 5 to 1, and also stated that: “Another referendum, a delay beyond the European elections, taking no deal off the table or not leaving at all would betray the 2016 people’s vote and damage democracy and our party for a generation.”

Q&A What is the Malthouse compromise? Show The Malthouse Compromise is named after housing minister Kit Malthouse, who brokered cross-party talks between Brexiters and former remainers on a possible way out of the Brexit impasse. The result involves redrafting the backstop arrangement for the Irish border which is so unpopular with Conservative Eurosceptic MPs and the Democratic Unionist party, which props up the government. It would also extend the transition period, set out under the previously negotiated withdrawal agreement, until the end of 2021. The extension is designed to give extra time to agree a new trading relationship. Under the plan, the backstop would be replaced with a free trade agreement with as yet unknown technology to avoid customs checks on the Irish border. If the attempt to renegotiate the backstop fails, the Malthouse compromise proposes what amounts to a managed no deal. The PM would ask the EU to honour the extended transition period, in return for agreeing the £39bn divorce bill and its commitments on EU citizens’ rights. This would give both sides time to prepare for departure on WTO terms at the end of 2021 – or to negotiate a different deal. The compromise is backed by the DUP, the European Research Group of hard Tory Brexiters, and former remainers including Nicky Morgan. However, the EU has repeatedly stated that the terms of the Withdrawal Agreement are not open for renegotiation

Fortunately, the alternative arrangements working group (AAWG) – which first met in January – has already considered the way forward without the withdrawal agreement. It has come to be called the “Malthouse Plan B”. In this scenario, both the EU and UK agree to minimise any disruption, ensuring that trade continues without the withdrawal agreement. The government has already put in place such measures and MEPs have voted on a number of “mini-deals”, including an arrangement for British car certifications to continue, permission for the EU to sell the UK their goods as a third country, an aviation deal to allow flights to continue and a road haulage deal.

This is not perfect but, as my AAWG colleague Nicky Morgan said, “It would allow time for both parties to prepare properly for WTO terms, but also provide a period in which the parties could obviate this outcome by negotiating a mutually beneficial future relationship.”

We need to remember, also, that no deal on 30 March is not an end state. Under article 24 of the WTO’s general agreement on tariffs and trade, so long as the UK and EU agree to a free trade agreement (FTA) and notify the WTO of a sufficiently detailed plan and schedule for the FTA as soon as possible, we could even maintain our current zero-tariff, zero-quantitative restrictions arrangements, while the new deal was being negotiated.

Malthouse B provides a clear route forward. It delivers Brexit on time and is without prejudice to the nature of the final agreement. MPs must bear this in mind if they are tempted to “take no deal off the table” in the vote today. That outcome would remove all the compression from future negotiations. Worse still would be a vote to extend the article 50 period. In practical terms, it is completely unclear what that would resolve, or if the EU would even agree to it. But, more than that, it would utterly shatter public trust in parliamentary democracy.

Voters in some 75% of Conservative seats at the last election had voted leave in 2016. How will any future candidate hope to win a seat if we have comprehensively reneged on our promises? How will Labour ever seek to form a government again if it pushes for an extension? Of the 100 Conservative seats with the smallest majorities in which Labour came second in 2017, 78 voted leave. Of those, 73 were more strongly for leave than the national picture. Over half of them have majorities of less than 5,000. What chance will a Labour candidate have in any of those?

If MPs do not take the path offered by Malthouse B and opt instead to drag on the uncertainty with an extension, the public verdict will be simple: on the single biggest issue of the age, parliament could not be trusted to deliver what people wanted.

• Conservative MP Owen Paterson is a member of the ERG and a former environment secretary