Conservative MPs who previously voted for the UK to remain in a customs union with the EU have told BuzzFeed News that they will now vote against any customs union amendment this week.
In a sign that attempts by rebel MPs to amend the government’s Withdrawal Agreement Bill to add a customs union could struggle to win a majority, the Democratic Unionist Party also signalled it would not support a customs union.
Staying in a customs union would remove the need for customs-related checks between the UK and the EU, including in the Irish Sea. As things stand, Boris Johnson’s deal takes the UK out of the customs union.
At the series of indicative votes held on various different Brexit plans back in April, MPs voted by a majority of three against a customs union with the EU.
Rebel MPs are likely to table an amendment to Johnson's withdrawal agreement this week to try to soften it by keeping the UK in a customs union.
It is expected that the Scottish National Party — which abstained in the April indicative vote — could vote for a customs union amendment.
But four MPs who voted for a customs union in April told BuzzFeed News that they had now switched against the idea, and would oppose the amendment this week.
Former Cabinet minister Damian Green said: “I won’t [vote for a customs union amendment], partly because now we have a deal which should get through the Commons.”
He added: “The time to discuss the CU is during the next stage of negotiations on the Trade Deal.”
Andrew Mitchell said he would now vote against a customs union because of the "very different circumstances". Backbencher Paul Masterton, who also backed a customs union last time, also said he would now vote against.
“This argument is for future relationship discussions, not a tool to be used to try and derail the deal being agreed,” Masterton told BuzzFeed News. “We should be testing to see whether we have a majority for the Prime Minister's deal on a straight vote before anything else.”
Fellow former customs union supporter Mark Pawsey said: "I won’t support a customs union amendment. The time for that has now passed and the priority is to get the deal through."
And former Tory rebel Richard Benyon, who voted for a customs union in April, told BuzzFeed News he would now oppose it.
"It's an attempt to wreck the Withdrawal Agreement," he said.
Two current Cabinet ministers, Nicky Morgan and Robert Buckland, voted for a customs union in April. They will now vote against it this week. Another Tory MP and previous customs union supporter, Victoria Prentis, told Sky News she would now vote against.
A number of senior Tory MPs, including Theresa May, Sajid Javid, Michael Gove, Gavin Williamson, and Steve Barclay, abstained on the vote in April. They will also vote against.
Labour MP Ann Clwyd, who previously voted against a customs union, said she would switch the other way and now back one.
Whether or not a customs union amendment has a majority this week could come down to how the DUP decides to vote.
On Monday morning, DUP MP Jim Shannon told Sky News that his party would not support a customs union.
It is not yet confirmed whether that is the official position of the party.
A Number 10 source told BuzzFeed News that Boris Johnson would not accept a customs union with the EU.
If a customs union amendment is successful, it is possible that the government could pull the Withdrawal Agreement Bill, agree an extension to Article 50 with the EU, and seek a general election.