'Progressive' politicians are failing to tackle Left-wing anti-Semitism because they won't tackle the 'unholy alliance' between parts of their movement and hardline Islamists, Tony Blair has warned.

The former prime minister said that figures on the Left are failing to confront extremists who see all Jews as supporters of Israel and the Netanyahu regime and therefore 'fair game' for violence and intimidation in the wake of the Israeli war in Gaza.

His intervention comes after an arson attack that destroyed four Jewish community ambulances in Golders Green, north London, last week.

Sir Tony, who is now involved with Donald Trump's Board of Peace initiative, said that while people were free to criticise Israel for its actions in killing thousands, they were failing to criticise the Hamas terror attack which triggered the war, and the group's actions during the fighting.

Writing for CBS chief executive Bari Weiss's The Free Press blog, he said: 'The problem is that, under pressure from party activists and parts of the Muslim community, many progressive politicians who do sincerely reject anti-Semitism are not making these arguments, and failing to take head-on this literally "unholy alliance" between parts of the Left and Islamists in our own societies whose ideology leads inexorably to anti-Semitism.

'Because failure to do so creates the climate in which, even if anti-Semitism is not explicitly condoned, it flourishes.'

He also warned that 'without a challenge to the ideology that encourages anti-Semitism, while clothing it in indignation at the human cost of war, incidents like the one with the ambulances will continue to the shame of our society'.

Last month Sir Tony said Trump's vision for peace in Gaza is its 'best' and 'only hope' as he spoke at the first meeting of the US President's Board of Peace.

The former prime minister is among those on the Gaza Executive Board, its operational arm.

The US President's peace plan would see Hamas and other factions agree to not have any role in the governance of Gaza.  

'For decades Gaza's governance has been characterised by extremism, corruption, ineffective institutions and the complete absence of a route to prosperity for the Gazan people,' the former PM said.

'Yet, as President Trump recognised, its potential has always been vast – 25 miles of Mediterranean coastline, proximity to great regional and global markets and a young, dynamic population with a median age of 19.

'So today we set out profound changes necessary to rebuild Gaza for Gazans.'

Two men – aged 47 and 45 and of British nationality – were detained on suspicion of arson with intent to endanger life over the Hatzola incident.

They have been bailed until April while the investigation continues.

Hatzola was founded in 1979 to provide emergency medical response to patients in north London at no cost.

It is run by volunteers who are trained by medical professionals who work alongside hospitals in the area, such as The Royal London, Homerton and Whittington hospitals.

The head of the Metropolitan Police has said the force was investigating whether an Islamist group with possible Iranian state links was behind the arson attack.

Gas canisters kept in the ambulances exploded after they were set alight, with nearby homes evacuated as a precaution.