Zack Polanski is now less popular with voters than Nigel Farage, a devastating poll has suggested on the eve of his crucial fight to win the Holborn and St Pancras by-election.

Fresh polling from More in Common has found Mr Polanski is the least popular major UK party leader, falling by four points to a -28 net approval.

His net approval sits four points below Mr Farage at - 24, while Andy Burnham has received a five-point boost to his approval ratings to +16 and Kemi Badenoch has risen by two to +2.

Overall, the poll found just 16 per cent of voters thought Mr Polanski was doing a good job as leader, compared to 43 per cent who believed he was doing a bad job.

Meanwhile, 28 per cent believed Mr Farage is doing a good job, compared to 52 per cent who believe he is doing a bad job.

The blow comes just ones day before voters in Holborn and St Pancras head to the polls to decide whether to elect Mr Polanski as their next MP after Sir Keir Starmer announced he was standing down.

But the fallout of a motion passed at the Green Party conference on Sunday, determining zionism as racism, has threatened to split the party.

It declares the Greens to be an “anti-Zionist party” and sets into its policy that Zionism, the movement to develop and protect a Jewish state in Israel, will be “treated as any other form of racism”.

In the wake of the vote, the Wales Green Party’s deputy leader announced his resignation on Tuesday, and said that he had left the party after seven years.

In a statement released late on Monday, Mr Polanski said the Green Party will “not accept any exclusion” of people based on religion.

“Antisemitism and criticism of the Israeli state are, and must always be, completely distinct – blurring the line between the two is not only wrong but antisemitic, and makes Jewish people less safe,” he said.

Mr Polanski, speaking at the party’s conference in Brighton, appeared to temper hopes of a Green win on Friday, saying his position as leader “doesn’t depend on it [winning the by-election] whatsoever.”

Mr Polanski abstained from the vote, having already left the conference to return to campaigning in Sir Keir Starmer’s old constituency.

Labour has held the Holborn and St Pancras seat continuously since it was created in 1983, but voters there have moved towards Green and independent candidates in recent years.

In May’s local elections, the Greens also saw major success, with Zoe Garbett becoming the UK’s first directly-elected Green mayor in Hackney – ending decades of Labour power in the position. Hours later, the party won another mayoralty in Lewisham.

Labour lost three councils to the Greens, including Hackney, Waltham Forest and Norwich, and also became the largest party in Lambeth. They also swept up Hastings council which was previously under no overall control.

But support for the Greens surged in his first year as leader, but the party’s national polling has dipped since Mr Burnham replaced Sir Keir in Downing Street.