David Cameron has admitted to MPs that he was wrong to accuse an imam of being an Islamic State supporter.
Muslim leaders called on the Prime Minister to apologise in the Commons after Sulaiman Ghani faced death threats as a result of his "smears".
But the premier chose a rarely used parliamentary device to set the record straight in writing instead of taking to the despatch box.
It comes after Downing Street said last night that Mr Cameron was sorry for "any misunderstanding".
In parliament's official record this morning, the PM said: "I was referring to reports that Mr Ghani supports an Islamic state. I am clear that this does not mean Mr Ghani supports the organisation Daesh and I apologise to him for any misunderstanding."
Defence Secretary Michael Fallon apologised on Wednesday for his "inadvertent error" in echoing the comments. Mr Ghani is in discussions with lawyers over possible legal action.
The Muslim Council of Britain called on the Conservatives to launch a probe into Islamophobia in the party.
Secretary general Shuja Shafi said: "As a result of these smears, we understand that Imam Ghani has been subject to abuse and threats on his life."
In the run-up to the local elections, the Prime Minister used question time in the Commons to accuse Labour's London mayoral candidate Sadiq Khan of repeatedly sharing a platform with Mr Ghani, a former imam at Tooting Islamic Centre.
Mr Cameron told MPs: ''Sulaiman Ghani, Mr Khan has appeared on a platform with him nine times. This man supports IS."
His comments were made under the protection of parliamentary privilege.
Dr Shafi urged the Tory party to learn from the "disreputable" campaigning.
He said: "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.
"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.
"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.
"We urge the Conservative Party to reflect and learn from this disreputable period of campaigning so that we can all draw a line and move on."