A Labour frontbencher denounced one of the party's key Brexit policies in a questions session at a think-tank, a recording obtained by the BBC reveals.
Barry Gardiner used colourful language to rubbish the party's pledge to secure the exact same benefits as the single market after Brexit.
He said the party should have instead said they would hold the Tories to account over their pledge to do that.
Leader Jeremy Corbyn said Mr Gardiner "fully supports" their Brexit policy.
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Speaking after the audio recording emerged, Mr Corbyn said: "Barry Gardiner does not denounce Brexit policies. We've had a conversation with him. It's quite clear he does support our strategy of holding the government to account on the tests that have been put forward.
"The conversations we've had with Barry more recently have been very productive and very positive."
In the recording of the event in Brussels last month, Mr Gardiner was asked about the "six tests" Labour set the government to decide whether to support the final Brexit deal in a Commons vote. He said: "Well let's just take one test – the exact same benefits. Bollocks.
"Always has been bollocks and it remains it.
"We know very well that we cannot have the exact same benefits and actually it would have made sense – because it was the Tories that said they were going to secure the exact same benefits – and our position should have been to say they have said they are going to secure the exact same benefits and we are going to hold them to that standard."
He said that should have been the Labour policy rather than saying "we think we can secure the exact same benefits as well".
The shadow international trade secretary made the comments after a speech at a think-tank in Brussels last month.
Responding to Mr Gardiner's comments, a Labour Party spokesperson said: "Labour has set six tests for the final Brexit deal. Those include holding the government to its own commitment to deliver the same benefits as the single market and customs union.
"We have been clear that, if those tests are not met, Labour will not back it in Parliament. Barry Gardiner fully supports that position."
The six tests were set out by shadow Brexit Secretary Sir Keir Starmer in March last year.
The second test was: "Does it deliver the exact same benefits as we currently have as members of the single market and the customs union?"
In February, Labour leader Jeremy Corbyn announced a shift in policy, committing the party to membership of a customs union after Brexit, but not the single market.
He said: "Labour would seek a final deal that gives full access to European markets and maintains the benefits of the single market and the customs union… with no new impediments to trade and no reduction in rights, standards and protections."
In an article for the Independent last month, Sir Keir said: "Labour will not support a deal that fails to meet the six tests I set out last year."
Labour's six tests for a Brexit deal
- Fair migration system for UK business and communities
- Retaining strong, collaborative relationship with EU
- Protecting national security and tackling cross-border crime
- Delivering for all nations and regions of the UK
- Protecting workers' rights and employment protections
- Ensuring same benefits currently enjoyed within single market
Labour MP Chris Leslie, a supporter of the cross-party Open Britain group, which campaigns against a "hard Brexit", said: "Barry Gardiner's increasingly maverick behaviour must be embarrassing for his frontbench colleagues."
He added: "Labour's policy, agreed by the party conference, is very clear: without the exact same benefits being on offer in any final Brexit deal, Labour would keep the option of staying in the EU on the table.
"It is time members of the shadow cabinet started speaking out for that and ended the sort of eccentric self-indulgence of the type shown by Barry Gardiner."
In remarks made at the same Brussels event, Mr Gardiner appeared to play down the risks of failing to resolve the border issue post-Brexit, and suggested both the Irish government and Sinn Fein may be exaggerating them.
"We must also recognise there are real economic reasons why people have played up the issue of the Irish border and the need to have the shibboleth of the Good Friday Agreement," he said.
Shibboleth means a long-standing custom, principle or way of speaking which identifies people as a member of a group – and in some modern uses it carries the implication of being outmoded or no longer important.
Following criticism from Labour's former shadow Northern Ireland Secretary Owen Smith and ex-leader Tony Blair, Mr Gardiner issued a statement insisting he "absolutely" does not believe the agreement was outdated.
He said: "I am deeply sorry that my informal remarks in a meeting last month have led to misunderstanding on that point – in particular, that my use of the word 'shibboleth' in its sense of 'password' or 'test of membership' gave the impression that I thought the Good Friday Agreement was in any way outdated or unimportant. I absolutely do not."