David Cameron has been forced to make a grovelling apology in Parliament to a cleric who he wrongly labelled an Islamic State-supporting extremist.

During the bitter battle to become Mayor of London, the Prime Minister attacked Labour candidate Sadiq Khan for appearing at events alongside the former imam Suliman Gani.

The premier told MPs: “Suliman Gani, Mr Khan has appeared on a platform with him nine times.

David Cameron (left) has been forced to make a grovelling apology in Parliament to Suliman Gani (right), a cleric who he wrongly labelled an Islamic State-supporting extremist

‘This man supports IS. He even shared a platform ... I think they are shouting down this point because they don’t want to hear the truth.

‘Anyone can make a mistake about who they appear on a platform with. We’re not always responsible for what our political opponents say. But if you do it time after time after time it is right to question your judgment.’

However, it has since emerged that comments which the PM was relying upon to support his claim were wrongly interpreted.

Mr Gani had spoken in support of the creation of an Islamic state - but, crucially, not the Islamic State terror group, also known as Daesh.

Defence Secretary Michael Fallon could face a big legal bill after Suliman Gani announced he was suing the Cabinet minister over claims he supports ISIS

This morning Mr Cameron issued a short statement in Parliament to 'clarify' his comments, telling MPs: ‘I was referring to reports that Mr Gani supports an Islamic state.

'I am clear that this does not mean Mr Gani supports the organisation Daesh and I apologise to him for any misunderstanding.’

Mr Gani had challenged Mr Cameron to make the accusations outside of the House of Commons, where he would not be protected by parliamentary privilege and could be taken to court over any defamatory allegations.

Mr Gani has already started legal proceedings against Defence Secretary Michael Fallon over claims he supported ISIS.

The Tory Cabinet minister could face a significant legal bill and Downing Street refused to say this morning whether the taxpayer would be forced to foot the costs.

Mr Cameron's apology to MPs today came after Tory MP Keith Simpson asked him to 'clarify his recent remarks concerning Suliman Gani'.

No10 and the Tory candidate Zac Goldsmith have been roundly criticised for the way the London contest was conducted. It ended on Friday night with a resounding victory for Mr Khan, who became London’s first Muslim mayor.

The Conservative campaign focused on alleged links between Mr Khan, a former human rights lawyer, and Islamist extremists. Mr Goldsmith’s own sister, Jemima Khan, distanced herself from the tactics.

But it has since been pointed out that Ghani supports the idea of an Islamic state, leading the PM to make a grovelling apology. Pictured: Khan attends the signing ceremony for the newly elected Mayor of London

As the result was announced on Friday, Tory peer Sayeeda Warsi, the first female Muslim minister to attend Cabinet, Tweeted: ‘Our appalling dog whistle campaign for London Mayor lost us the election, our reputation & credibility on issues of race and religion.’

A string of other senior Tories savaged the Goldsmith camp. The most senior Conservative in the London assembly, Andrew Boff, said the tactics used by the Goldsmith camp were ‘ridiculous’ and had ‘blown up’ bridges with the Muslim community.

He said the approach would damage integration in London and was a ‘bizarre’ thing for a London politician to do.

‘I don’t think it was dog whistle because you can’t hear a dog whistle - everybody could hear this,’ he said.