UKIP's under-fire Scottish MEP David Coburn, who is facing calls to quit after muddling an SNP minister's name with a terrorist cleric, allegedly persistently mispronounced the name of an Asian rival during last year's European elections.

David Coburn is already facing resignation calls after referring to SNP minister Humza Yousaf as "Abu Hamza", the extremist preacher.

Now it has been claimed that during his successful European Parliament campaign, Mr Coburn routinely muddled the first name of Tasmina Ahmed-Sheikh, an SNP candidate.

Mr Coburn and Ms Ahmed-Sheikh were both chasing the sixth and final Scottish Euro seat. The UKIP victory was the party's first and only electoral breakthrough north of the border.

Ms Ahmed-Sheikh said: "During last year's European election campaign, I was faced with David Coburn's ignorance as he repeatedly got my name wrong.

"During the days and weeks of the campaign he called me Pashmina, Jasmine and Tamzin before eventually settling on a combination of 'love', 'dear' and 'honey'.

"I found his remarks sexist - and possibly racist.

"We need to be doing all we can to encourage women and people of black and minority ethnic origin into politics.

"Mr Coburn is a dinosaur, and if his leader Nigel Farage has a shred of decency he will sack him now."

Mr Yousaf first called on Mr Farage to sack Mr Coburn this weekend after the MEP's Abu Hamza "joke" was revealed in a tabloid.

The external affairs minister described the remark as an "Islamophobic slur" that left him feeling "deeply hurt".

He said: "It is quite unbelievable for anyone to think it is appropriate to compare me to a convicted terrorist simply because I am a Muslim.

"None of us would tolerate this behaviour if we witnessed this being shouted at a Muslim in the street - but the fact it has come from an elected member of the European Parliament is beyond the pale."

Scottish opposition leaders, including Labour's Jim Murphy and the Conservatives' Ruth Davidson, echoed widespread condemnation of any comparison between Mr Yousaf and Abu Hamza, who is currently jailed in America on terror charges.

Mr Coburn himself did not take calls on Sunday to defend himself. When The Herald tried to contact him, he hung up while a television in the background played the Match of the Day theme tune.

However, UKIP's Scottish chairman, Misty Thackeray, insisted that no offence had been intended to either Mr Yousaf or Ms Ahmed-Sheikh, who is currently standing for the SNP in Ochil and South Perthshire.

Mr Thackeray said: "How humourless and thin-skinned are these people trying to make faux outrage stories about a slip of the tongue over a name?"

Asked about Mr Yousaf's resignation call, he said: "It is a complete non-story. Somebody gets a name wrong and people are talking about resignations? Absolutely bizarre: this is not a resigning matter."

Mr Thackeray also denied that Mr Coburn had routinely got Ms Akhmed-Sheikh's name wrong.

He said: "It wasn't mispronounced throughout the entire Euro campaign. "It was mispronounced once; if memory serves me correctly, David called her Jasmina."

UKIP insiders have suggested that the party had a tactic - jokingly dubbed "Operation Trashmina" - to throw the SNP candidate off her stride in TV debates and hustings by saying her name wrongly.

Mr Thackeray denied this, saying Operational Trashmina was an "interesting phrase but not one I would recognise".

He added: "I am not going to comment on hearsay from people who don't give their name and who are no doubt opponents within the party.

"Our membership is up and our funding is up and we have more candidates in this general election than ever before, so I certainly can't fault David Coburn's first year."

Mr Thackeray and Mr Coburn are standing for Westminster in Scottish seats, Glasgow East and Falkirk respectively.

Their leader, Nigel Farage, this weekend offered to support a minority Tory Government after May's general election.

Mr Yousaf wrote to Prime Minister David Cameron urging him to rule out a pact with UKIP.

The MSP wrote: "UKIP have crossed the line of common decency and stepped into the murky waters of racism, bigotry and religious hatred, where they are now firmly entrenched.

"It is simply inconceivable that any mainstream political party could even contemplate doing any sort of post-election deal with them."