David Miliband has issued a call for politicians on all sides to fight back against the “worst consequences” of last year’s vote for Britain to leave the EU.

The former Labour Foreign Secretary described the outcome of the 2016 referendum as an “unparalleled act of economic self-harm”.

Writing in The Observer, he said the country should have the chance to vote on any Brexit deal in a second referendum, with a straight choice between remaining in the EU and the negotiated alternative.

“People say we must respect the referendum. We should. But democracy did not end on 23 June, 2016. The referendum will be no excuse if the country is driven off a cliff,” he wrote.

“MPs are there to exercise judgement. Delegating to Theresa May and David Davis, never mind Boris Johnson and Liam Fox, the settlement of a workable alternative to EU membership is a delusion, not just an abdication.”

His intervention came as Chancellor Philip Hammond and International Trade Secretary Liam Fox came together to declare that a post-Brexit transition would not be a “back door” to Britain remaining in the EU.

After a summer of cabinet feuding, Mr Hammond, who favours a “softer” pro-business Brexit, and Mr Fox, a hardline Brexiteer, said that they agreed there should not be “cliff-edge” break when Britain leaves the EU in March 2019.

In a joint article for The Sunday Telegraph, they said any transition would be “time limited” and that Brexit would mean the UK pulling out of both the EU single market and the customs union.

In pictures: European parliament Brexit discussions Show all 12 1 /12 In pictures: European parliament Brexit discussions In pictures: European parliament Brexit discussions European commission member in charge of Brexit negotiations with Britain, French Michel Barnier listens at the President of the European Commission Jean-Claude Juncker speaking at the European Parliament in Strasbourg Getty Images In pictures: European parliament Brexit discussions Frank-Walter Steinmeier, President of the Federal Republic of Germany, delivers his speech at the European Parliament in Strasbourg EPA In pictures: European parliament Brexit discussions European Union's chief Brexit negotiator Guy Verhofstadt, President of the Group of the Alliance of Liberals and Democrats for Europe (ALDE), addresses the European Parliament during a debate on Brexit priorities and the upcomming talks on the UK's withdrawal from the EU Reuters In pictures: European parliament Brexit discussions Michel Barnier, European Chief Negotiator for Brexit reacts during a meeting at the European Parliament in Strasbourg EPA In pictures: European parliament Brexit discussions Member of the European Parliament and former leader of the anti-EU UK Independence Party (UKIP) Nigel Farage wears socks with Union Jack flag at the European Parliament in Strasbourg Getty Images In pictures: European parliament Brexit discussions Nigel Farage, United Kingdom Independence Party (UKIP) member and MEP, addresses the European Parliament during a debate on Brexit priorities and the upcoming talks on the UK's withdrawal from the EU Reuters In pictures: European parliament Brexit discussions European commission member in charge of Brexit negotiations with Britain, French Michel Barnier gestures during speeches at the European Parliament in Strasbourg Getty In pictures: European parliament Brexit discussions The President of the European Commission Jean-Claude Juncker (L) speaks with European commission member in charge of Brexit negotiations with Britain, French Michel Barnier at the European Parliament in Strasbourg Getty In pictures: European parliament Brexit discussions European Union's chief Brexit negotiator Guy Verhofstadt, President of the Group of the Alliance of Liberals and Democrats for Europe (ALDE), addresses the European Parliament during a debate on Brexit priorities and the upcomming talks on the UK's withdrawal from the EU Reuters In pictures: European parliament Brexit discussions Member of the European Parliament and former leader of the anti-EU UK Independence Party (UKIP) Nigel Farage gestures during speeches at the European Parliament in Strasbourg, eastern France, on April 5, 2017. The European Parliament will on April 5 lay down its "red lines" for negotiations over a Brexit deal, on which the assembly will have the final say in two years' time. / AFP PHOTO / Sebastien BozonSEBASTIEN BOZON/AFP/Getty Images Getty In pictures: European parliament Brexit discussions German president Frank-Walter Steinmeier delivers a speech during a plenary session at the European Parliament in Strasbourg Getty In pictures: European parliament Brexit discussions The European Parliament in Strasbourg, eastern France Getty Images

“We want our economy to remain strong and vibrant through this period of change. That means businesses need to have confidence that there will not be a cliff-edge when we leave the EU in just over 20 months’ time,” they wrote.

“That is why we believe a time-limited interim period will be important to further our national interest and give business greater certainty – but it cannot be indefinite; it cannot be a back door to staying in the EU.

“We are both clear that during this period the UK will be outside the customs union and will be a ‘third country’, not a party to EU treaties.”

Prime Minister Theresa May will hope the intervention of the two ministers will cool temperatures in the Tory ranks amid divisions over Brexit and speculation of a possible leadership challenge when MPs return to Westminster in September.

However, the leading Conservative Remainer Anna Soubry warned the Prime Minister that she needed to face down the “hard Brexiteers” in the Conservative ranks if she wanted to hold on to her position in No 10.

“Mrs May is making a great mistake if she allows her policy to be dictated by the Brexit ideologues. They effectively brought down John Major, David Cameron and, arguably, Margaret Thatcher – and will not hesitate to do the same to her,” she said in an article for The Mail on Sunday.

The former business minister also indicated that she could be prepared to join with politicians from other parties to stop the country “staggering recklessly” towards a hard break with Brussels.

“Could I ever see myself joining with like-minded people who want to save our country from such an appalling fate? And has that moment arrived yet?” she wrote.

“The answer to the first question is ‘it is not impossible’; the answer to the second is ‘no’. But I would be betraying my principles if I did not make it clear that country must always come before party.”

In his article, Mr Miliband stopped short of following the former Conservative aide James Chapman in calling for pro-Remain MPs to come together in a new party.

He did, however, back cross-party calls – supported by Conservative Lord William Hague and Labour's Heidi Alexander and Stephen Kinnock – for Britain to remain in the European Economic Area free trade zone along with Norway, Iceland and Liechtenstein as well as the EU member states.

“In Britain, the implementation of the EU referendum decision has been rash and chaotic. The timing and content has been governed by factions in the Tory party. Our negotiating position is a mystery – even on immigration,” he wrote.

“So the fightback against the worst consequences of the referendum has the opportunity and responsibility to get its bearings fast.”