The Scottish Labour leader, Richard Leonard, has said his party must keep the “Bernie Sanders” faction onside and build the broad coalition of support needed to win a general election, as it ramps up campaigning before May’s elections. He also called for a “swift resolution” to the suspension of Jeremy Corbyn over the former leader’s response to an equalities watchdog investigation into antisemitism in the party. Leonard, who has faced challenges to his leadership and whose party is polling as low as 12% in Scotland, is aligned with supporters of Corbyn. In an interview with the Guardian, Leonard said he believed his party could overtake the Conservatives in Scotland, and the SNP would face a “reckoning” over the coronavirus pandemic. He said Labour could learn lessons from Joe Biden’s victory in the US, both in terms of party unity and in campaigning. “I think it is clearly about trying to bring together a coalition. It seems to me that the Biden coalition was pretty wide and was able to encompass the Bernie Sanders faction, which I would probably identify myself more closely with,” he said. “But he clearly got a huge response from parts of American communities that hadn’t voted Democrat for some time.” Leonard said the “vote early” message of postal voting was also a key lesson. “In the midst of a pandemic, how you organise is going to necessarily be different. And having such a controversial opponent really helped solidify people’s resolve to do something to make a change.” He urged Labour to come to a resolution over Corbyn’s suspension so that the party could focus outwards. “The Labour party just needs to get over some of its differences. I make no secret of the fact that there have been challenges to me and to my leadership,” he said. “The Labour party should always be looking outward. It’s always been a danger of being caught up in inward-looking debates.” He said the party’s procedures for dealing with complaints and grievances was “extraordinarily slow”, adding: “I think one of the comments of the EHRC [antisemitism] report was about inaction and delay … I think the swift resolution of Jeremy’s suspension would be extremely helpful for everybody.” His call for an inclusive coalition within Labour will raise eyebrows among his critics. When a small group of MSPs called for him to quit and tried to force a leadership contest in September, Leonard said they could face deselection or be barred from standing in May’s Holyrood election. Leonard will face a test in the run-up to the Scottish parliamentary elections in May, where the SNP are expected to make sweeping gains and drive momentum for a second independence referendum. He admitted that Sturgeon’s gamble to make herself the face of the pandemic had paid off, with a surge in support for the SNP and for independence. But he said this popularity masked huge errors and called for a Scotland-focused public inquiry. “They see her [Sturgeon], you know, frankly, in juxtaposition to Boris Johnson. That is boosting their ratings and, indeed, boosting support for independence,” Leonard said. “She’s decided that she is going to be the face and the voice of Scotland’s response to the pandemic. “I think that there will be a point of reckoning on things like what happened in Scotland’s care homes. For a lot of the summer, 50% of all Covid-related deaths were in care homes. And that wasn’t just something that’s happening all over Europe, as Nicola Sturgeon claims. This is something which happened at the … guidance, issued by the Scottish government.” He said Sturgeon and Johnson were “two sides of the same coin” in terms of fuelling support for independence, and he described Johnson as an “English nationalist” whose own support for the union was in question. “We don’t underestimate the Boris Johnson effect,” he said. “I have to say to people: you couldn’t possibly take a decision as profound as whether you want to separate out from the rest of the UK or remain in the UK based on the fact that Boris Johnson is the prime minister, because he’s transient. This is a huge decision, which has got massive long-term consequences, economic, social and otherwise.” Labour is likely to face a dilemma in the face of an overwhelming SNP victory over whether it should support calls for a second referendum – something Leonard does not yet want to concede. “Our position going into the election next year is that we are not for a second referendum. Even amongst people that support independence, many of them say that’s not the priority,” he said. “In the next five years the parliament should really be focused on dealing with real and existing crises that we face. Even if it were to happen that the referendum parties got a majority, do people want, you know, three, four years of a wrangle with Boris Johnson about that? “We need to see urgent action on the issues of the day. We just do not see the case for further big constitutional debate, division and upheaval.”