Politicians and Muslim leaders have called on Ukip MEP David Coburn to resign for allegedly comparing SNP minister Humza Yousaf to convicted terrorist Abu Hamza.
Mr Yousaf, the Scottish Government's Minister for Europe and International Development, said he was "appalled, disgusted and hurt" by the "Islamophobic" comment reported in the Scottish Daily Mail.
The MSP for Glasgow has written to Ukip leader Nigel Farage calling for Mr Coburn to be suspended while an investigation takes place.
First Minister Nicola Sturgeon condemned the alleged remark as "reprehensible" while Scottish Labour leader Jim Murphy said it was "sickening and senseless" and Scottish Conservative leader Ruth Davidson described it as "totally unacceptable".
The Muslim Council of Scotland (MCS) said Mr Coburn is "not fit to represent Scottish people in the European Parliament".
But Ukip's Scottish chairman, Arthur Misty Thackeray, denied the comparison had been made, saying his party colleague made a "slip of the tongue " and "got a name wrong".
Mr Coburn, Ukip's only elected member in Scotland, is said to have made the remark during a conversation with the paper regarding his appearance on the BBC's Big Immigration Debate on Tuesday.
He is reported to have claimed that Mr Yousaf was supposed to appear on the show, before stating: "Humza Yousaf, or as I call him, Abu Hamza, didn't seem to turn up."
The MEP, who is standing for Ukip in the Falkirk constituency at the general election, is said to have told the paper that the remark was intended to be private.
Mr Coburn has made no comment today.
Mr Yousaf said: "If this was shouted at a Muslim on the street, none of us would tolerate it. The fact this abuse has come from an elected member of the European Parliament is even more shocking and completely unacceptable.
"Nigel Farage has been plagued by accusations of leading a racist party and this outburst from David Coburn MEP shows that Ukip are not just a party with a few rotten apples but rotten to the core.
"If Nigel Farage is serious about Ukip being a party that will not tolerate xenophobia in any form, then I expect David Coburn to be expelled from Ukip immediately and have written to Nigel Farage in that vein."
He added: "David Coburn has been exposed making Islamophobic remarks and should do the honourable thing and resign."
The First Minister said: "This is an appalling and reprehensible thing to say.
"For David Coburn to effectively compare Humza to a convicted terrorist because he is Muslim is disgraceful and he must surely face consequences for that."
Mr Thackeray said: "This is a non-story. David Coburn did not compare Humza Yousaf to convicted terrorist Abu Hamza.
"He simply got a name wrong, which many people do on a daily basis. For example, I very often get referred to as Minty, which I believe is a character from EastEnders, but I don't take offence at that and run greeting to the papers about Mistyphobia.
"I just accept that sometimes people get a name wrong. It simply was a slip of the tongue. "
Radical cleric Hamza was sentenced to life in prison for a string of terrorism offences by a judge in New York in January.
Last year a jury found him guilty of supporting terrorist organisations, including aiding the taking of hostages in Yemen and seeking to set up an al Qaida training camp in the United States.
Hamza, previously from north London, was jailed in the UK for seven years for soliciting murder and inciting racial hatred in 2006 and first faced an extradition request from the US in 2004.
MCS spokesman Mazhar Khan said: "The fact that Ukip is no stranger to such controversy and has regularly been accused of having racists within its ranks only exacerbates the offence.
"To prove its rejection of intolerance and Islamophobia, MCS calls on Ukip leader Nigel Farage to do the right thing and take immediate action against David Coburn, such a person is not fit to represent Scottish people in the European Parliament."