Green Party leader Zack Polanski has been selected as the party’s candidate in the by-election for Sir Keir Starmer’s former seat in Parliament.

Polanski, who is a London Assembly member, will stand in Holborn and St Pancras on 8 October as he seeks to become an MP.

He was voted to be the party’s candidate by members of the Camden Green Party ahead of local councillor Hamza Chowdhury.

Polanski said the Greens “might be the underdog in this election but we have the momentum and we can win”.

He also spoke of how he made Camden “my home” when he first moved to London 20 years ago, adding he has “lived and worked across Holborn and St Pancras for many of the years since”.

Polanski said: “I love this place but I also know times are tough here in Holborn and St Pancras. My story of constantly moving around flats is such a common story for Londoners and I know so many people are struggling right now.”

He argued that voting Green “sends a clear signal” to the council and government that “we demand better for our communities”.

Polanski added he is “confident but not complacent” about his chances.

He also said the election is about “putting pressure” on Prime Minister Andy Burnham, noting a Green MP would “work with him constructively to challenge him on the gaps in his plans”.

Announcing the result, Green MP Hannah Spencer said members had “overwhelmingly” chosen Polanski.

The Greens finished second to Labour at the elections for Camden Council earlier this year.

The by-election is an early test of Burnham’s popularity with the public and whether Labour under his leadership is able to fend off the challenge from the Greens in inner-city constituencies.

For Polanski, it will be a test on whether he can provide evidence that he can deliver on his ambition for the Greens to “replace” Labour.

Labour has held the inner London seat since it was created in 1983 and the party’s candidate for the by-election is Camden Council leader Sagal Abdi-Wali.

The seat became vacant after former Prime Minister Sir Keir announced he was standing down as an MP to focus on a role in international affairs.