An influential union leader has warned that Labour faces an “existential crisis” in Scotland as rebels tabled a no-confidence vote in the party leader, Richard Leonard. Gary Smith, the secretary of GMB Scotland, said the crisis over the party’s leadership and its plummeting popularity in Scotland raised profound questions about Labour’s future at UK level, with polls putting its support as low as 14%. The GMB helped finance Leonard’s leadership campaign in 2017, giving him £12,000 and a free “phone bank” to canvass members. Leonard was a senior GMB officer for 20 years before becoming a Labour MSP in 2016. He remains a GMB member. Smith said the union would not intervene on Leonard’s behalf. The GMB has refused to support his tenure as leader or back the rebellion led by a group of party centrists. Smith indicated most GMB members voted for the Scottish National party. “At a time like this, our members would not thank us for getting bogged down in an internal Scottish Labour party issue, a party for which many of them no longer vote for,” he said. “The truth is Scottish Labour’s problems run far deeper than one individual. It is facing an existential crisis in Scotland and the knock-on effect for the UK party could be quite profound.” Smith’s comments came as the rebels confirmed they had tabled a confidence motion for a meeting of Labour’s Scottish executive committee (SEC) on Saturday, which has been signed by a third of the committee’s 32 members. They hope to force Leonard to resign or get the Scottish executive to agree to a leadership contest, but Leonard said on Friday morning he would resist their demands. He accused them of fighting a factional war at a time when many Labour policies were being adopted by Nicola Sturgeon’s government. “The last thing Labour supporters and those we need to win back want to see is a party turning in on itself,” Leonard said. “A lot of these people are not mandated by their organisations to vote in this way. “That exposes how this is motivated by faction and that this is an entirely factional move. They have nothing to say or offer, no ideas, no plan to protect jobs and living standards against the backdrop of the Covid crisis.” Leonard’s critics, led by James Kelly, whose resignation last week as Labour’s justice spokesman triggered the rebellion, argue the party’s collapse in support threatens Sir Keir Starmer’s chances of winning a UK general election. They argue the electoral arithmetic dictates Labour has to win back significant numbers of seats in Scotland to win a majority at Westminster. It currently holds one seat. Leonard’s critics also argue few donors will fund Labour’s Holyrood election campaign in May if he is still leader, making it more likely the SNP will win a majority and demand a second Scottish independence referendum. They believe the UK party will be unable to fully fund a Scottish campaign because its finances will be highly stretched with simultaneous election campaigns in Wales, regional mayoral contests and council elections, including for the Greater London assembly. The rebels expect the no-confidence vote to be extremely close, but Leonard has won public backing from two other key unions, Unite, Scotland’s largest, and Unison, and the former veteran Labour MEP David Martin, bolstering his confidence. Those unions each have two votes on the SEC, as does the GMB. Unite gave Leonard £30,000 for his campaign in 2017 and phone bank support, while Unison donated £9,000. Usdaw, the shop workers’ union, also has two votes on the SEC and gave Leonard £5,000 but it has not yet said where it stands on his future. Pat Rafferty, Unite’s Scottish secretary, told the Sunday Post last weekend: “Voters will be repelled by this sort of conduct. They want to see their MSPs focused on supporting communities and saving jobs, not indulging in underhand efforts to dislodged an elected leader. Whoever is organising this disgraceful coup should pack it in at once.”