BRITAIN will crash out of the the customs union immediately after Brexit, two leading Cabinet ministers have declared, saying they will not commit to a transitional period that will lead to the the UK staying in the EU by the “back door”.

Liam Fox, the International Trade Secretary and a keen Brexiteer, and Chancellor Philip Hammond, possibly the most pro-Remain Cabinet minister, used a joint article in The Sunday Telegraph to say they had put aside their differences over what should happen when the UK leaves the EU in March 2019.

The customs union effectively means that once goods have cleared customs in one of the countries signed up, they can then be shipped to the others without any further tariffs. The big advantage of this for the UK is that the border between Ireland and Northern Ireland remains open and easy to cross.

However, continuing membership would stop Britain being able to make bilateral trade deals with non-EU countries.

This was one of the big battles in the Cabinet. When Hammond said last month that “many things will look similar” during the post-Brexit transitional period, which expected to last three years at least, some of his colleagues felt he was trying to delay Britain leaving the EU.

Some Brexit supporters worried that if the UK remained in the customs union during this transitional period the arrangement would be end up becoming permanent, leaving the UK as some form of associate member.

Yesterday’s article shows that the Brexiteers have won that argument, with Hammond having to concede the transition cannot be a “black door to staying in the EU”.

The two ministers wrote: “We respect the will of the British people – in March 2019 the United Kingdom will leave the European Union. We will leave the customs union and be free to negotiate the best trade deals around the world as an independent, open, trading nation. We will leave the single market, because there was a vote for change on June 23 and that is what we will deliver.

“When we’ve left the customs union, we will build upon [relationships with other countries] by negotiating as an independent nation with the freedom to sign bilateral free trade agreements.”

Stephen Gethins, the SNP’s Europe spokesperson at Westminster, said the article showed it would be up to Scottish MPs to stop a hard Brexit. “Despite the contrived efforts of Theresa May’s top lieutenants, there is no masking the fact that there are deep divisions within her own Cabinet over Brexit – and still no apparent plan almost 14 months on from the vote.

“While the Brexiteers are still manning the helm, there are clear doubts over the course being taken and the potential damage to jobs, trade, our economy and living standards. At Westminster, Scottish MPs could hold the balance in ensuring Scotland’s place in the single market is protected.

“Ruth Davidson and Kezia Dugdale should remind themselves of what they said in the immediate aftermath of the EU referendum about fighting tooth and nail to ensure Scotland continues in the single market. They should have the courage of their convictions, show some leadership, and give their MPs at Westminster one clear objective – to put Scotland’s interests first."