Monica Lennon, a contender for the Scottish Labour leadership, has said support for independence could increase if Labour fails to accept a fresh referendum may be needed. Lennon, a candidate backed by the party’s left, said more voters would desert Labour and back independence if they saw the party lining up with Boris Johnson by refusing to accept the case for a referendum. Anas Sarwar, the leadership frontrunner, has rejected calls to back a new referendum, but Lennon said pro-independence parties would have a mandate to hold a fresh vote if they won a majority of Holyrood seats in May’s Scottish elections. “If people in Scotland through the ballot box express that they want a referendum, it would be foolish and undemocratic to ignore that,” Lennon told the Guardian. One could be held within the five-year lifetime of the next parliament, but not this year, as some SNP leaders have suggested. “It would be irresponsible for anyone to race ahead and force a referendum to happen this year while we’re still in the middle of a pandemic,” she said. “But for those people who want to hide behind Boris Johnson [by rejecting one], then I would say that would be a disaster for Scottish Labour and actually that itself puts the union at risk. I believe the biggest threat to the union is Boris Johnson and the Tories.” Lennon leapt to prominence last year after MSPs backed her private member’s bill to make Scotland the first country in the world to provide free period products. Vogue magazine then made her one of 12 women who changed the world in 2020, alongside the US vice-president, Kamala Harris, and Jacinda Ardern, the prime minister of New Zealand. Elected to Holyrood in 2016, Lennon, a former council planning officer, said Scottish Labour could only win back voters who swung behind the SNP over the past decade if it acknowledged many believed in independence. The failure to do so after the 2014 independence referendum led to Labour being “wiped out” in the 2015 Westminster election, losing 40 seats. “We’ve been losing people’s trust and confidence for a long time, and it takes a while to put that back together,” she said. Lennon said she wanted to prevent the SNP and the pro-independence Scottish Greens winning a majority in May. But if that failed and a referendum was organised, Labour should instead campaign for a federal option on the ballot as an alternative to independence, she said. That could be similar to proposals in a federalism blueprint commissioned by Jeremy Corbyn, the former UK party leader, she said. It advocated replacing the Lords with an elected senate and substantial new powers for the UK’s devolved parliaments and English regions. “We’re sounding very grumpy about the constitution,” she said. “We’re telling people it’s irresponsible to be talking about it. But they’re going to talk about it anyway; they’re going to talk about it without us. I’m standing to lead the party because I’m sick and tired of Scottish Labour being left behind, talking to ourselves.” Sarwar has said it is “deeply irresponsible” to support another independence referendum, and believes Labour should focus solely on the pandemic, combating the deep recession and attacking Nicola Sturgeon’s domestic policy record. He and other Labour figures admit, however, the party has been too slow to offer counter-proposals to independence. Keir Starmer’s plans to unveil a UK-wide constitutional convention in January were delayed when Richard Leonard suddenly resigned as Scottish Labour leader, triggering the current contest. The winner is due to be announced on 27 February. Lennon said Labour should already be campaigning to devolve employment and drugs legislation to Scotland, so Holyrood could scrap restrictive trade union laws and decriminalise drugs to tackle the country’s record rates of drug deaths. The absence of a compelling alternative from Labour, she said, meant many voters had moved towards independence: 21 opinion polls in succession have shown a yes majority, excluding don’t knows. “Because Scottish Labour haven’t been showing that there’s a better way, then people are being asked to respond to opinion polls that give them a binary choice between independence, which involves jumping off a cliff, or staying with what we have, which a majority of people don’t like,” she said.