The group of Labour rebels hoping to topple Richard Leonard as party leader in Scotland have begun the process of mounting a challenge after he refused to quit voluntarily. Two Labour MSPs, James Kelly and Daniel Johnson, told party officials in Glasgow and London that five MSPs were willing to call for a leadership contest, claiming Leonard has failed to command the support of voters and party activists. Kelly and Johnson wrote to Michael Sharpe, the Scottish Labour party’s general secretary, and the party’s governance and legal unit in London to clarify what its rules were on calling leadership elections if a leader refuses to quit. Kelly launched the rebellion last week by resigning as the party’s frontbench justice spokesman, followed several hours later by Mark Griffin, the social security spokesman. Johnson and Jenny Marra, another backbench MSP, supported their calls for Leonard to quit. Over the weekend, Leonard and his allies said there were no processes in the Scottish party’s rules that allow a leadership challenge to take place if there is someone in post; and he described the rebels as mounting an “internal war” on his leadership. Speaking on Sky on Sunday, Leonard said his critics had underestimated his resolve, and that Labour’s decline was a long-term problem he had inherited. Labour’s support has slumped to 14% under his leadership, and the party lost six of its seven Scottish seats in the 2019 Westminster election. The letter from Kelly and Johnson, passed to the Guardian, argues that the Scottish party should be bound to follow the UK party’s rules, which allow for a contested leadership ballot to take place if 20% of Labour parliamentarians support it. They claim to have passed that threshold in the Scottish parliament, and want to trigger that contest if Leonard again refuses to step down voluntarily. In a statement late on Tuesday, Sharpe said there was nothing in the Scottish party rulebook that allowed for a challenge to an incumbent leader; the UK party’s rules only applied to UK leadership posts. “This is a rule for that element of the Labour party, but it is not a ‘precedent’ for the Scottish Labour party,” Sharpe said. “A precedent might be a past action or decision of the Scottish Labour party which helps interpret our rules. However, I am not aware of any such precedent on this issue.” Johnson and Kelly hope the UK party’s legal department will agree with their argument that the UK rules should apply in the absence of any Scottish rules on a leadership challenge. In their joint letter, the MSPs wrote: “We are taking this action as we believe that Labour party democracy, underpinned by clear rules that are consistently applied, is vitally important. “We reject the implication that, once installed, the leader of the Scottish Labour party enjoys indefinite tenure. This is not democratic and goes against our party’s fundamental principles and values. “This action has been driven by sorrow, not anger, after Richard Leonard has failed to command the support of MSPs, Labour activists and most importantly, the Scottish people. “We are pleading with Richard, once again, to put our party first and to stand aside so that we can start the urgent work to regain the trust of the Scottish people ahead of next year’s election under a new leader.”