A leading pro-European Labour MP has called on Jeremy Corbyn to sack any shadow ministers who refuse to support a second Brexit referendum.

Ian Murray, a prominent supporter of the People’s Vote campaign, said the Labour leader needed to prove his commitment to a referendum by telling his MPs to back the measure in any Westminster vote, or else face sanctions.

Many pro-EU Labour MPs suspect Corbyn has been forced into reluctantly supporting a second referendum and could fail to properly enforce the policy when the amendment calling for one is put to the Commons. It has been proposed by two Labour backbenchers, Peter Kyle and Phil Wilson.

“The problem with the Kyle-Wilson amendment is this: it will only pass if the Labour front bench enthusiastically support it, whip it, then we win it,” Murray told a fringe event at the Scottish Labour party conference in Dundee on Saturday.

Corbyn offered only lukewarm support for a referendum in his Scottish conference speech on Friday, and is being lobbied hard by competing groups at Westminster.

Many Labour frontbenchers and MPs have expressed doubts about a fresh referendum, and some shadow ministers who fear alienating pro-Brexit voters have suggested they would resign if forced to back it.

More than a dozen shadow cabinet ministers, including the shadow housing minister, Melanie Onn, and the shadow justice minister, Gloria De Piero, warned against backing the fresh vote in January. Equally, Corbyn has been told to expect up to 10 frontbench resignations if he fails to press for it.

Support at Westminster for a second referendum is delicately balanced, with its supporters acknowledging that they do not yet know whether they would win a Commons vote on the amendment. Much hinges on the votes of the Scottish National party, which has 35 MPs, and anti-Brexit Tory MPs.

The timing of the amendment is seen as crucial. Pro-referendum strategists want to delay a Commons vote on it until MPs see it as the only feasible alternative to a no-deal Brexit, which will be the case if Theresa May, as expected, loses the final vote on her deal.

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The Kyle-Wilson amendment was originally expected to be tabled on Tuesday, when May’s deal is put to a vote. That option is now in doubt, although the amendment could resurface later next week.

In an article for the Guardian, Alastair Campbell, Tony Blair’s former head of communications, said Tuesday “must belong to Mrs May being made to see her deal will not – and cannot – fly”.

Richard Leonard, the Scottish Labour leader, sought to reinforce his pro-Europe credentials and heal the splits in the party by telling conference delegates that he supported a second referendum.

After an angry dispute about the lack of a conference event to mark the contribution of Labour MEPs who face losing their posts after Brexit, Leonard told the last two Scottish MEPs, David Martin and Catherine Stihler, “You are a credit to our party, so I thank you from the bottom of my heart.”

As yet, no Labour MP or MSP has joined the breakaway Independent Group of dissident MPs. Leonard said he disliked splits, and that Labour was a tolerant and democratic party that welcomed dissent. However, he also warned critical MPs that they were not elected on their own, and owed a debt to the party as a whole.