The Tories have come under further criticism for the campaign run by Zac Goldsmith against Sadiq Khan in London with the Muslim Council of Britain calling for an investigation into “Islamophobia” in the party.

This comes after Labour backbencher Chuka Umunna condemned Theresa May for signing a letter that said London would be less safe with Khan as mayor, and David Cameron was forced to apologise to a London imam for falsely claiming he supported ISIS. The claim became an integral part of the botched effort to link Khan to Islamic extremism.

Dr Shuja Shafi, secretary general of the Muslim Council of Britain, welcomed Cameron’s apology to Sulaiman Ghani, but demanded an urgent review of what he described as “Islamophobia” in the Conservative Party. He also called on Cameron to reiterate his apology in the House of Commons, where his claims about Imam Ghani were made.

Shafi said: “I welcome the Prime Minister’s long overdue apology to Imam Sulaiman Ghani, a London imam who has thus far been unable to challenge claims made in Parliament that he supports Daesh or terrorism. As a result of these smears, we understand that Imam Ghani has been subject to abuse and threats on his life.

“I call on both the Prime Minister and the Defence Secretary to make that apology in Parliament as well. Imam Ghani became the innocent casualty of a wider Islamophobic attack on the now Mayor of London and the Conservative Party needs to apologise for this too.

“Such smear-by-association has become all too common for Muslims and Muslim organisations. It is a cancer blighting sections of our political and media class and has infected the solemn business of government.”

He added that actions like this had a knock-on effect of helping radicalisation, by painting even moderate Muslims as extreme.

“For the real extremists we are all opposed to, such tactics will only provide fresh new examples of a society not willing to accept Muslims for who they are,” he said.

“I also call for an urgent review of Islamophobia in the Conservative Party. Just as the Labour Party is rightly conducting an inquiry into anti-Semitism, it is important for the Conservative Party to reflect upon the extent of Islamophobia in its own ranks. We should have zero tolerance for both anti-Semitism and Islamophobia.”

A Downing Street spokesman told the Independent: “In reference to the Prime Minister’s comments on Sulaiman Ghani, the Prime Minister was referring to reports that he supports an Islamic state. The Prime Minister is clear this does not mean Mr Ghani supports the organisation Daesh and he apologises to him for any misunderstanding.”

Fallon apologised yesterday for his “inadvertent error” over his comments about Ghani.

In a Home Affairs select committee briefing this week, Umunna also hit out at Theresa May for supporting the campaign, asking her whether she believed London was unsafe with Khan as Mayor – a question she refused to answer.

You can see their exchange below: