Zack Polanski refused to say Israel has a right to exist today and branded Zionism a 'racist ideology' that has been responsible for ethnic cleansing of Palestinians today.
The Green Party leader said that the ideology that supports the creation of a homeland for Jews was synonymous with 'basic colonialism and racism' in Gaza and the West Bank.
He made the remarks as he faced the cameras for the first time since a major anti-Semitism row engulfed his party.
He has faced both internal and external criticism of his leadership after the Green Party conference in Brighton backed a motion describing Zionism as 'racism' in a vote Mr Polanski did not take part in.
The policy called for Israel to be treated like apartheid-era South Africa and ultimately replaced by a Palestinian state with Jerusalem as its capital.
Appearing on the BBC's Sunday with Laura Kuenssberg he said and while he did not agree with the policy he would not seek to change party rules to amend the policy before 2028, when it can next be put to a vote.
Asked if he believed that Israel had a right to exist he said: 'I don't think any country has a right to exist.'
'There is no right to exist for any country ... people have a right to exist.'
The Green Party leader said that the ideology that supports the creation of a homeland for Jews was synonymous with 'basic colonialism and racism' in Gaza and the West Bank
Asked about whether he believed Zionism was racist, he cited thousands of deaths in Gaza at the hands of the Israeli Defence Force (IDF), saying: 'When you take that into account, the fact that they are being murdered because they are Palestinian, that is very obviously a racist ideology.'
Asked about his views on Zionism more broadly, Mr Polanski, who is himself Jewish and grew up in a Zionist family, said that argument was 'semantics'.
When it was pointed out that some people believed it was an ideology that searched for a safe homeland for Jews, he went on: 'I think that is what people think it means, but actually in practical application, which is what we are talking about here, that homeland has come at the cost of the Palestinian people.
'I want equal rights for Israelis and Palestinians. The practical application of Zionism has not resulted in that.'
The decision taken at the party conference has seen the leader of the Jewish Greens, Vivien Lichtenstein, call for Mr Polanski to resign and say she is considering leaving the party.
Labour has also issued an ultimatum to local Green groups it is currently in coalition with, telling them to disown the motion or lose the party's support.
Just days after the conference decision, Mr Polanski suffered a further setback when he was defeated at the Holborn and St Pancras by-election.
It came as a new poll showed Mr Polanski has slumped to his worst poll rating as Green leader amid the row.
An October survey by Ipsos found 52 per cent of the public said they had an unfavourable view of the Green leader, up six points since September and the first time more than half the population had expressed a negative opinion of him.
Just 16 per cent said they had a positive view of Mr Polanski and his overall rating has fallen to minus 36, the lowest rating of any national party leader.
Much of the opposition to Mr Polanski is concentrated among older groups, the poll suggested.
But he has also lost ground among under-35s, falling from a net score of plus 16 in April to just plus two.
His support among people who voted Labour in 2024 has also plummeted, from a net favourability of plus seven in April to minus 24 in October.
Keiran Pedley, UK director of politics at Ipsos, said the public had noticed that it had been a 'bruising month' for Mr Polanski.
The Ipsos poll, conducted in the immediate wake of that by-election, found Andy Burnham remained the only senior UK politician with an overall positive favourability score.
The Prime Minister enjoys a net favourability score of plus eight, while Kemi Badenoch's score is minus 12 and Sir Ed Davey's is minus 15.
Reform UK leader Nigel Farage's overall score is minus 31, with some 56 per cent of people saying they have an unfavourable view of him.
Mr Pedley added: 'Andy Burnham appears to be in the ascendancy for the battle for hearts and minds on the left, with 2024 Green voters almost as positive towards him as the leader of the Green Party itself.'
The Ipsos poll surveyed 2,257 British adults online between October 9 and 13.