The Greens have been embarrassingly forced to return a donation from leader Zack Polanski - because he was not on the electoral register.

Mr Polanski gave £1,539.45 to the London branch of his party on September 23 last year.

But it was deemed impermissible because he did not feature on the roll of voters at the time - something a spokesperson blamed on 'personal security concerns'.

Labour accused Mr Polanski of failing to know 'basic' information about political rules. 

To be lawful donations to political parties must be made by people on the electoral register. If found to be impermissible they must usually be returned within 30 days.

The Financial Times reported the money was given back to Mr Polanski only on June 10 this year after it was reported to the Electoral Commission on October 28 last year.

The watchdog is currently considering the case under its regulatory remit but no official investigation has been launched.

A Green Party spokesman said that 'at the time of this donation, Zack was not on the electoral register because of personal security concerns'.

'When the issue was brought to the national party's attention the donation was returned,' they added.

Mr Polanski swept to victory in the Green leadership race three weeks before making the donation, having previously stood as a councillor for the Liberal Democrats before switching parties in 2017.

It is not the first time he has drawn scrutiny over his electoral status. Last month, he admitted he had not voted in the local elections because he 'fell short of time' to register while moving house.

The party said he would have needed to go through extra steps in the registration process to cast a ballot anonymously, citing security concerns after he became 'the target of antisemitic and homophobic abuse'.

In a statement regarding the impermissible donation, the Electoral Commission said: 'The guidance makes clear that the law requires donees to report impermissible donations and return them to the donor within 30 days.

'If after the 30-day period they become aware that a donation they have accepted is impermissible, they should act quickly to bring themselves into compliance.

'The donee should return the value of the donation to the donor if possible, or to the commission.

'We are currently considering this under our regulatory remit, so we cannot comment further at this time. This is not the subject of an investigation by the commission.'

Labour chair Anna Turley said Mr Polanski had a 'track record of thinking the rules don't apply to him'.

'Now it turns out that he tried to make a political donation of over £1,500 without being registered to vote in the UK - a basic requirement which anyone in his position should know about,' she said.

'Polanski wants people to think he receives an unfair level of scrutiny but it's only right that the public know when politicians haven't been following the rules. It's the least the British people should be able to expect from those seeking high office.'