The shadow trade secretary, Barry Gardiner, has laid bare the continuing tension on the opposition frontbench about Labour’s approach to Brexit. Speaking at a Prospect/Port of Dover fringe event at the party’s conference in Liverpool he warned that it was “looney tunes territory” for anyone to imagine Theresa May rushing to concede an early general election in the event of the Commons voting down her Brexit deal—even though it is official Labour policy to demand one. The remarks could set him on a collision course with Jeremy Corbyn and John McDonnell, who have been working towards a delicate compromise with the party’s membership.

The main media focus of the Liverpool conference has been on a dispute between largely pro-Remain members, who are trying to persuade Labour to endorse a second in/out referendum on the final Brexit deal, and the party leadership and certain union leaders, such as Len McCluskey, who are anxious this would alienate voters in Labour’s many northern and midland constituencies that plumped for Leave in 2016. A long meeting on Sunday night produced a carefully-worded motion which stresses the party’s preference for a general election in the event of the government’s Brexit plans hitting the rocks, and adds that “if we cannot get a general election Labour must support all options remaining on the table, including campaigning for a public vote.”

Gardiner, however, was entirely dismissive of the prospect of any hope of a second election, pointing out that Conservative MPs would be certain to veto any attempt at dissolution under the terms of the Fixed-term Parliaments Act, even if “by any miracle” May were to follow her ruinous decision to stage an early election last year by proposing another. He also made clear that he thought there would be no legal obligation on the government to concede a so-called “people’s vote” even if the Commons were to vote down May’s deal using a motion that demanded such a referendum.

While Gardiner said he would love an election and would cheerfully vote to Remain in any new referendum, people were in “looney tunes territory” if they thought the government would be rushing to concede these things. He said that in recent weeks, he had been talking to the Commons clerks about the consequences of the government’s Brexit plans being voted down, and he had concluded that there were very few ways in which MPs would be able to bind ministerial hands. A “non-fatal” amendment to May’s plans could potentially end up in the courts, and even a “fatal” amendment would be unlikely to be able to dictate what she did after the defeat.

Gardiner stressed he is now very worried about a catastrophic no-deal Brexit, which he insists is what the Tory right have been plotting all along. He argued that Labour’s agreed policy on “a customs union” with the EU would offer a way out of the impasse revealed at the Salzburg summit, by solving the two sticking points which prevented the rest of Europe from being able to agree to May’s Chequers plan—specifically, the situation on the Irish border and post-Brexit arrangements regarding the collection of duties.

Gardiner suggested—controversially—that by agreeing to a customs union with Europe, both problems could be solved. He observed that Conservative MPs including Nicky Morgan, Anna Soubry and Dominic Grieve had previously amended government legislation to insist on such a union before backing off on voting for this change. And he proposed that Labour should make clear to May that “she had a potential majority in the House of Commons” if only she would adopt Labour policy on this point.

The implication of Gardiner’s remarks is that Labour should be ready to back May on her deal if she prepares to make this concession to the opposition, something the shadow trade secretary regards as unproblematic because “of course we would vote for Labour policy.” Again, however, this looks like a departure from colleagues—including the shadow foreign secretary Emily Thornberry—who have come close to saying they will vote against any deal that May can produce.

Many years ago, I worked at the DTI where Gardiner was a junior minister. He was always forensically engaged with the detail, and unafraid to argue his corner on specific points of policy, even if doing so was seen as inconvenient to the department, No 10, the Treasury or anyone else.

Since 2016, he has emerged as a more senior figure within Labour—one of increasingly few MPs with ministerial experience in the New Labour years who are still happy to serve on Corbyn’s front bench.

In the context of Brexit, he has previously adopted stances that have been controversial within his party, including by coming out strongly against single market membership and also full membership of the existing “customs union” (in a very subtle distinction from the frontbench’s current position on “a customs union”). He has also been reported as saying that people were “playing up” the notorious Irish border complications of Brexit for their own reasons.

During Monday afternoon’s fringe, Gardiner joked about his established tendency to “go off the piste.” Despite all the arguments he has picked over tactics with many of the most strident of Labour’s pro-Europeans, he was clear, however, that he continued to regard Brexit itself as a mistake. It was for him, he said, still fundamentally a “question of self-harm” and how to minimise that.