Three other shadow cabinet ministers abstain in protest against three-line whip to back fresh vote

Jeremy Corbyn’s shadow housing minister has resigned and three shadow cabinet ministers abstained in protest against a three-line whip to vote in favour of plans for a second referendum.

Melanie Onn confirmed she had resigned to vote against the option in the ballot of MPs on Wednesday and the shadow cabinet ministers Jon Trickett, Ian Lavery and Andrew Gwynne all abstained to register their discomfort with the plan.

Labour confirmed on Wednesday that it would expect MPs to support a motion, tabled by Margaret Beckett, which said parliament should not ratify any Brexit deal “unless and until” it has been approved in a “confirmatory public vote”.

Corbyn wrote to Labour MPs on Wednesday afternoon stressing that his party’s first priority was “to deliver our credible Brexit plan” in an attempt to avert a wave of resignations from his frontbench.

But the Labour leader was already facing a fierce backlash from a group of shadow cabinet ministers, many of them strong supporters of his leadership, who are wary of supporting a measure that appeared to be aimed at overturning Brexit.

Onn was among 27 MPs who rebelled and voted against the amendment, including the mayor of the Sheffield city region, Dan Jarvis, as well as other vocal referendum sceptics Caroline Flint, John Mann and Gareth Snell.

Eighteen more MPs abstained, including the three shadow cabinet ministers and others including Tracy Brabin, Stephen Kinnock and Lisa Nandy.

Corbyn was visited earlier on Wednesday by sceptical colleagues including Gwynne, Lavery, Trickett, Angela Rayner and Rebecca Long-Bailey, after which he issued his letter to Labour MPs.

He wrote: “Labour’s proposed deal remains our preferred solution: based on a customs union, close alignment with the single market and dynamic alignment on rights, standards and protections.”

Corbyn told MPs the party was supporting Beckett’s proposal, “even where it can be read as going beyond our policy”, to “keep the option of a public vote on the table in order to stop a disastrous no deal or May’s unacceptable deal”.

One shadow minister had earlier warned that Labour would face “a very significant rebellion” if it tried to force MPs to back the motion, and another said: “If we whip for it, we won’t have a shadow cabinet by the end of the day.”

However, the Guardian understands that most shadow cabinet ministers agreed to support the amendment, on the condition that the letter was sent; although some junior frontbenchers were still considering their options.

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However, there was also a angry comeback on Wednesday morning from the pro-referendum wing of the party against an interview by the shadow international trade secretary, Barry Gardiner, in which he said Labour was “not a remain party now” and that it could have difficulty supporting a motion for a referendum on any Brexit deal.

Gardiner also suggested Labour was concerned that the motion could suggest the party would allow Theresa May’s deal to pass if it led to a referendum.

“It would be saying we could accept what we have always said is a very bad deal. Therefore it looks as if the attempt to have a public vote on it is simply a way of trying to remain because nobody likes this deal,” Gardiner told BBC Radio 4’s Today programme.

“To put that up as the only alternative in a public vote and say we will let it go through looks as though you believe that, at the end of it, remain would be the result. It is not where our policy has been.

“Our policy is clearly that we would support a public vote to stop no deal or to stop a bad deal, but not that we would allow a bad deal as long as the public had the opportunity to reject Brexit altogether.”

He said Labour could not be portrayed as a party that wanted remain at any price. “We have accepted the result of the referendum,” he said.

Labour’s deputy leader, Tom Watson, tweeted within the hour that he supported the referendum approach and later pushed Corbyn to impose strict discipline on Labour MPs who defied the whip and failed to vote for the amendment on Wednesday evening.

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Corbyn’s spokesman confirmed the party would whip for Beckett’s “confirmatory public vote” option – as well as the one put forward by Snell and Ken Clarke, calling for a customs union, and the one setting out Labour’s own Brexit policy.

He said whips would also be “encouraging” Labour MPs to support common market 2.0, the cross-party proposal drawn up by Labour’s Kinnock, among others.

Asked if shadow frontbenchers would be sacked if they disobeyed the whip, he said: “The discipline arrangements are a matter for the chief whip.” But he stressed that the indicative votes process was “unusual”.

No decision is expected to be made until Thursday about the future of the shadow cabinet ministers who abstained, but a Labour spokesperson said the circumstances “are exceptional,” a hint that they may face no sanction.

“It’s clear we need to find common ground in parliament to stop either a disastrous no deal Brexit or the prime minister’s botched deal,” the spokesman said. “Labour is well placed to lead these efforts as our MPs represent constituencies that voted both leave and remain. It is now a matter for the leader and the whips.”