Zack Polanski is facing a sleaze inquiry as questions mount over his council tax arrangements and whether he broke electoral law.
The Green Party leader, who is a member of the London Assembly, has been reported to City Hall's sleaze watchdog over concerns about his council tax liability for the past three years.
The Mail has established that Mr Polanski was registered on the electoral roll at a building in a marina where he kept a narrowboat - despite maintaining he didn't live on the boat permanently.
The left-wing leader had post delivered to the same marina building in east London and regularly, over a number of years, had laundry collected from the canal barge he shared with his partner.
The narrowboat was recently advertised for sale for £100,000 - but the notice was pulled after Mr Polanski's council tax arrangements were questioned last week.
Mr Polanski, 43, maintains he only stayed on the boat 'occasionally', despite his partner referring to it as their 'amazing home' over the past three years in the advert.
Now the Tory leader on the London Assembly has reported Mr Polanski to City Hall's monitoring officer over his council tax arrangements and electoral roll registration.
The complaint, seen by the Daily Mail, calls for a formal investigation into 'Mr Polanski's residency arrangements, electoral registration, and potential council tax liability in relation to a narrowboat in east London'.
The Daily Mail has established that Zack Polanski was registered on the electoral roll at a building in a marina in east London where he kept a narrowboat
The narrowboat was recently advertised for sale for £100,000 – but the notice was pulled after the Green Party leader's council tax arrangements were questioned
Government guidance suggests that council tax may be payable if a boat is a person's 'sole or main residence'.
Analysis by tax lawyer Dan Neidle, from Tax Policy Associates, found that Mr Polanski and his partner's boat was not registered for council tax at the marina.
The boat and mooring would be rated as Band A, meaning a total council tax for three years of about £4,000 would be due if it was a 'main residence', the analysis adds.
However if Mr Polanski only stayed on the boat 'occasionally' then he may have breached electoral law by registering to vote at a property where he was not resident, Mr Neidle said.
Public records show that in 2025 Mr Polanski was registered on the electoral roll at the address in the marina. But the Lee Valley Authority, which owns the address, has confirmed that he did not rent the bungalow property at the water's edge.
The Green Party has so far declined to answer direct questions about whether Mr Polanski paid council tax for the past three years or where he was living, instead providing a vague response.
Neil Garratt, the leader of the City Hall Conservatives, said: 'If Mr Polanski paid all his council tax, why is he refusing to answer direct questions about when and where he paid it?
'I have asked the City Hall authorities to formally investigate these claims, as the public has a right to know the truth.'
The Green Party leader, who is a member of the London Assembly, has been reported to City Hall's sleaze watchdog over his 'residency arrangements, electoral registration, and potential council tax liability in relation to a narrowboat in east London'
The narrowboat was recently advertised for sale, with the since-deleted advert posted saying it 'has been our amazing home in the peace and quiet on the River Lea for three years'.
The ad stated that mooring fees are more than £750 per month and added: 'We are moving to a house and so will sadly be leaving the gorgeous community behind.'
The complaint to the City Hall sleaze watchdog adds: 'I wish to make a formal complaint concerning the conduct of London Assembly member Zack Polanski and request that you assess whether his conduct may amount to a breach of the Greater London Authority code of conduct…
'I believe these allegations are sufficiently serious to justify consideration under the GLA code of conduct and the Nolan Principles… in particular those relating to integrity, honesty, accountability, and leadership.'
On his register of interests for the London Assembly, the Green leader declares that either he or his partner 'alone or jointly' has a 'mooring in London'.
Mr Polanski recently told The Sunday Times that he and his partner rented a flat in Hackney.
The Green Party and a spokesman for Mr Polanski were approached for comment.
The Greater London Authority (GLA) said a complaint has been received by the monitoring officer and will be considered in due course.