Few things are more irritating, in politics, than pretending to a higher wisdom and morality than your opponents can ever hope to attain. This is the trap into which David Miliband, Nicky Morgan and Sir Nick Clegg have fallen with their claim, while warning against a hard Brexit, to be  “putting our country before our political parties”.

They seem unaware that this is what many politicians do. Over the last half century, many Eurosceptics have quite clearly put country before party.

On the other side, one might say that in 1981 the founders of the SDP put their idea of the national interest before the well-being of the Labour Party, which they deserted, or which they complained had deserted them. Roy Jenkins, Shirley Williams, David Owen and Bill Rodgers hoped, of course, that their new party would succeed, but no one can deny they took a big risk in launching it, or that Jenkins and Williams soon proved themselves formidable by-election candidates.

Do Miliband, Morgan and Clegg propose to form a new centre party? Will we soon see Miliband confounding his critics by sweeping to victory at a by-election in some unexpected seat in Glasgow?

It seems unlikely. For although a few journalists have wondered, rather half-heartedly, whether a new centre party is about to be formed, the Gang of Three are clearly more intent on influencing what happens within the existing parties. Here is Miliband on the Today programme this morning, addressing the leader of the party to which he still belongs:

“The warning for Jeremy Corbyn is that, if he is not very careful, he will be the midwife of a hard Brexit that threatens the living standards of the very people that he says he wants to represent.”

The tone again is one of unselfconscious arrogance. Miliband knows better than Corbyn how to run these complicated negotiations. He also knows better than Corbyn how to represent the people Corbyn claims to represent.

Which raises the obvious question of when Miliband – who had a safe seat in South Shields until 2013, when he stood down and went to work in New York – last talked to any British voters, and especially to Labour voters in the north-east of England who by a substantial majority supported the Leave side in the EU referendum.

The Gang of Three “call on Parliament to reject completely the siren calls to sever the UK’s deep economic ties with the European Union.”

But what sensible person wants to sever those ties? The aim is free trade, rebranded as “maximum facilitation”, for it is plainly in nobody’s interests for goods to stop moving freely across the English Channel, the Irish Sea and indeed the land border between Northern Ireland and the Republic.

A modicum of good will and pragmatism on both sides should enable that goal to be achieved. The slowness with which Theresa May is proceeding has already enabled quite a few Remainers, though clearly not the Gang of Three, to realise the situation is not developing in the disastrous way they were led to expect.

The British people want Parliament to get on and complete the process of Brexit, as decided in the EU referendum and promised by the main parties at last year’s general election. Two days ago, Theresa May reiterated, in an article for The Sunday Times,  her promises to take back control of our laws, borders and money, and to leave the Single Market and the Customs Union.

By urging her to stay in some form of Customs Union, the Gang of Three are inciting her to commit a breach of faith with the British people which neither she nor the Conservative Party would be likely to survive.