Zack Polanski will stand as the Green party candidate in the Holborn and St Pancras byelection slated for 8 October, the party confirmed on Friday. The announcement means local members voted to select Polanski over a surprise opponent, who ran against him from within his own party. Green councillor Hamza Chowdhury announced on Monday that he was also seeking nomination, arguing that as a Camden resident he would be better placed to represent constituents than the party leader, who lives in east London. Polanski’s selection comes just ten days after former prime minister Keir Starmer announced his resignation as MP and subsequent departure from the seat. The decision means that, a year on from becoming the Green leader, Polanski could be only weeks away from being catapulted into the House of Commons. But first he must face a high stakes contest against Labour – which won the seat with a more than 11,000 majority at the last general election – with the vote due to take place just a week after many Greens decamp to Brighton for the party’s annual conference. “The Greens might be the underdog in this election, but we have the momentum and we can win,” Polanski told a meeting to announce the party’s candidate on Friday. Asked by Novara Media whether he thought a Green win in Holborn and St Pancras would increase the chances of progressive announcements in the upcoming budget, Polanski said it would “make a huge difference”. “It would be a victory that would say that in this budget, Andy Burnham and John Healey as chancellor need to think about working people in this country – and indeed, people who are unemployed or disabled, people who are really, really suffering right now. “[Housing secretary] Angela Rayner ruled out rent controls. But I imagine that a Green victory would make the Labour government think pretty quickly again,” he gave as one example. Green membership has tripled from 68,500 to over 230,000 under Polanski’s leadership, and Hannah Spencer spearheaded the party’s first ever parliamentary byelection success in Gorton and Denton in February. But with a drop in Green voting intention since Andy Burnham became prime minister in July, an uphill battle looms. An all-time high of 21% of Brits said that they intended to vote Green in March, but that dropped to just 13% in August, according to YouGov polling. Holborn and St Pancras has been a Labour seat since the constituency’s creation in 1983. Its population has only been represented by two MPs: Frank Dobson from 1983 to 2015, and then Starmer, until earlier this month. Labour’s by-election pick is Sagal Abdi-Wali, the leader of Camden council. A child refugee from Somalia, Abdi-Wali grew up in the seat and is deeply concerned with tackling inequality. Polanski has also prioritised the issue, urging the government to bring in price caps to shield people from seismic energy bills, demanded an end to the two child benefit cap, and called for measures to protect people and food supplies from extreme heat and wildfires.