Andy Burnham has called on Green leader Zack Polanski to reverse a motion passed by members of his party declaring Zionism a form of racism.

The prime minister said the motion, approved on Sunday at the party’s conference in Brighton, was “completely wrong” and showed “terrible judgement”.

The motion defined Zionism as an ideology supporting “an ethnonationalist Jewish state” and backed a “single democratic Palestinian state in all of historic Palestine”, which includes modern-day Israel.

In the wake of the vote, Polanski has said he would not accept anyone being excluded from the Green Party “because of the religious or communal body they are part of”.

The Green leader has declined media interviews since the motion was passed and did not answer questions from a BBC reporter about the motion ahead of Burnham’s comments.

The former Green leader Caroline Lucas has criticised Polanski for not taking part in a debate and vote on the controversial motion.

Lucas told the BBC the jury was out on whether he would now show the leadership she believed was required.

She told Newsnight: “He should have been there and he should have voted.”

Lucas, who voted against the motion, added: “I would have hoped he would have been a very strong critic of this motion. The motion was flawed from top to bottom – in my view it is dangerous, it is divisive.”

Asked if Polanski should stand down, she said: “I think let’s just see what happens in the coming days and weeks. Obviously he has been completely taken up with this by-election.

“I want him to speak now about what’s happened, I want him to show the leadership that was frankly missing on Sunday. I think the jury is out about whether he will do that – but I very much hope he will.”

The controversy comes as polls close in Thursday’s Holborn and St Pancras by-election, in which Polanski is a candidate.

The motion has complicated the final days of Polanksi’s campaign in the contest, where the Greens have been looking to overturn a substantial Labour majority in the seat vacated by former Prime Minister Sir Keir Starmer.

It has sparked days of controversy, with four of the five Green MPs opposing it, its co-deputy leaders split on supporting it, the Green deputy leader in Wales resigning, and condemnation from members and Green counterparts in Europe.

Polanski did not vote on the Zionism motion, having left the conference early to return to London for the by-election campaign.

An amendment he had backed to specify that the motion should not be used to discipline Jewish members attending synagogues that consider themselves Zionist was voted down by members.

Before the vote, he had also said he wanted to see the reference to a single Palestinian state changed, arguing: “I don’t believe we as a Green Party of England and Wales, or even the British government, should be deciding what the future settlement looks like.”

The Green Party has an internal democracy model, under which official party policy is decided by members. However, these positions are not necessarily included in the party’s general election manifestos.

In his first intervention in the row on Thursday, Burnham said he felt the motion effectively ruled out a two-state solution between Israel and Palestine.

“For that reason, it shouldn’t be supported in any way, shape or form,” he told reporters while on a visit to Berlin.

“I would call on the leadership of the Green Party to say that it will be reversed and it won’t be Green Party policy.”

When asked if he would rule out entering into coalition with the party, he would not be drawn on “any business about what might or might not happen in the future”.

In a statement on Monday, Polanski did not specify whether he supported the motion passed by members but said he would not accept anyone being excluded from the party “because of the religious or communal body they are part of”.

On Thursday, a Green Party spokesperson said: “This has been an emotive issue and is complex. It has rightly caused much discussion, and needs to be taken in the context that Israel’s behaviour has had.

“Israel has been responsible for a genocide, ethnic cleansing and the killing of children, and we’ve had a political establishment which has not only turned a blind eye but provided support.”

The International Court of Justice (ICJ) is currently hearing a case brought by South Africa that accuses Israeli forces of genocide, but it could take years to reach a conclusion. Israel has called the case “wholly unfounded” and based on “biased and false claims”.

Sign up for our Politics Essential newsletter to keep up with the inner workings of Westminster and beyond.