Former business secretary Sir Vince said: "Trade negotiations are nasty, brutish and long, and they generally involve large trade-offs". Northern Ireland would form part of our customs territory.
"It is purely there in the circumstances where we've agreed the end state customs arrangement, but for technical reasons it's not been possible to put that in place by 1 January 2021".
And it calls for the arrangement to apply to the whole of Britain.
The EU's Brexit negotiator Michel Barnier welcomed the publication but stuck by the conditions that have led to a stalemate in the talks so far, and made clear Brussels would not accept any legal time-limit.
It would be used if a permanent customs deal is not in place at the end of the 21-month Brexit transition period, with the aim of avoiding a hard Irish border.
"Is it an all-weather backstop?" he said.
"We have made clear that, of the government's two proposed policies, the customs partnership represents nearly business as usual at the border for UK-EU trade, but whatever arrangement we choose it is vital there is time for ports to adapt to avoid disruption", Ballantyne said.
However, Barnier then rejected a recent United Kingdom government proposal for all of the United Kingdom to remain inside the customs union until an arrangement can be made that prevents the EU from imposing a so called hard border between Northern Ireland and the Republic of Ireland.
"A backstop that is temporary is not a backstop, unless the definitive arrangement is the same as the backstop", he added. Davis still claimed a victory, but other Brexit hardliners in the Conservative party were not satisfied.
"We could be in real crisis with no deal, which emphasises the importance of having a vote on the final package with the option of remaining in the European Union".
Michel Barnier also stated that Brussels would not be "intimidated" by Brexiteers who try to blame the bloc for not securing the Brexit deal they want.
"Of the eight demands made in FTA's list of essentials to "Keep Britain Trading", issued at the beginning of the year, not a single one has been progressed," he said.
"On the basis of the red lines we have, there is no solution", an unnamed senior European Union official told the Financial Times in April. We believe this is the right thing to do so that everyone's voice can be heard.
Mr Thompson said the high frequency of transactions meant firms would still have to fill in customs declarations. Both Davis's and PM Theresa May's camps declared victory.
A source close to Mr Davis said: "Obviously there's been a back and forth on this paper, as there always is when the government publishes anything".
The Prime Minister was "going to go into a phase where we are much more combative with Brussels", the Cabinet minister said.
"Instead, with the threat of a cabinet resignation, Theresa May has signed up to a flawed proposal which is inconsistent with her earlier commitments".
"It would tie us effectively into the EU's customs arrangement for an indefinite period", he said.
In an open letter to voters, Best For Britain warned that there was a danger of the political establishment "sleepwalking the country over the Brexit finish line" in March without any clarity over whether the deal will be good for the UK.
But, under pressure from her DUP allies at Westminster, the prime minister dismissed the plan, explaining it threatened the "constitutional integrity" of the UK.