Writing in the Sunday Telegraph, the two cabinet members said that "we are both clear" that during the period Britain would be outside the single market and the customs union "and will be a "third country" not party to EU treaties".

Chancellor Philip Hammond, a strong Remain campaigner, and Trade Secretary Liam Fox, a leading Brexiteer, put on a display of unity with a joint pledge that echoes Theresa May's oft-repeated remark that "Brexit means Brexit".

They write that there will be a "time-limited" transition period that would "further our national interest and give business greater certainty", but insist that Brexit will not be halted.

David Davis, the Brexit secretary said the publication of the papers, which will begin this week, would mark "an important next step" towards delivering last year's referendum vote to leave the EU. "When we've left the customs union, we will build up on [relationships with other countries] by negotiating as an independent nation with the freedom to sign bilateral free trade agreements". They said the UK's borders "must continue to operate smoothly", that goods bought on the Internet "must still cross borders", and "businesses must still be able to supply their customers across the EU" in the weeks and months after Brexit.

"Once the interim period is over, we want a permanent, treaty-based arrangement between the United Kingdom and the EU which supports the closest possible relationship with the European Union, retaining close ties of security, trade and commerce", Hammond and Fox said. "That means businesses need to have confidence that there will not be a cliff-edge when we leave the European Union in just over 20 months' time", they wrote. Irish Prime Minister Leo Varadkar said last week that Brexit advocates "already had 14 months" to issue detailed proposals, but had not.

The paper says that a "formal position paper to be published next week by the government" which will state that ministers are sticking with plans for a "light touch" customs border.

"Nobody voted to be poorer a year ago but that is exactly what will happen if the Government continues to put Eurosceptic dogma ahead of the national interest".

"We've been crystal clear that issues around our withdrawal and our future partnership are inextricably linked, and the negotiations so far have reinforced that view", the Department for Exiting the European Union said in the statement released on Sunday. We should. But democracy did not end on June 23 past year.

Negotiations between Brexit Secretary David Davis and European Union officials are set to resume at the end of this month.