AN SNP MSP has apologised profusely for using the word “fag” about a gay Scottish Conservative MP.

James Dornan, the MSP for Glasgow Cathcart, said he was “horrified” at his "booboo" after applying the term to Ross Thomson, the Brexiter MP for Aberdeen South.

The word means a younger pupil who carries out chores for an older one at a private boarding school, but is also a homophobic term of abuse.

Mr Dornan was criticised after using the word on Twitter on Saturday while discussing Old Etonian Boris Johnson becoming the next Tory leader and PM.

Mr Thomson is a public supporter of Mr Johnson.

The MSP said the former Foreign Secretary would would be “busy quaffing champagne and telling his new fag, my money is on Ross Thomson for that position, to keep still whilst he uses his back as a table.

“Honestly I don’t think he cares about Scotland at all.”

Other Twitter users questioned whether Mr Dornan had been homophobic.

Katie Frank, Mr Thomson’s head of office, tweeted: “Using homophobic comments is not okay. Politicians in the LGBT community get enough abuse as it is.

“Saying you have gay friends and family does not excuse using this language. The SNP must condemn this behaviour now. No excuses.”

Glasgow Tory councillor Thomas Kerr added: “Does James Dornan and John Mason have a bet on who can be the most outrageous MSP? What a nasty little man.”

Another Twitter user said: “I find this comment from James Dornan utterly repugnant. I hope Nicola Sturgeon & the SNP will denounce it.”

Responding to critics, Mr Dornan said on Twitter: “I honestly never thought for a second about that use of the word, never used it and never consider it. It’s about the public school practice. My apologies if anyone was upset by it, I’m horrified.”

He went on: “The truth is that never even entered my head... Never used it that way and never think that way. Too many friends and family are gay for me to even consider using a derogatory term for it. My apologies to those who never recognised the context.

“Even when I saw the few tweets criticising it I thought they were just sympathising with Ross, not having a go at me about sexuality.

"It makes perfect sense if a) you know Boris did go to public school b) ‘fagging’ is a well established, if ridiculous, practice and c) you’ve ever seen Ross fawn over Boris.

"I’ve already apologised for any misunderstanding of the use of the word. Not sure what else can be said."

Mr Dornan, 66, has been an MSP since 2011, and is currently convener of the Scottish Parliament’s local government and communities committee.

It emerged last month that he was one of a handful of MSPs to have snubbed a “culture of respect” workshop offered by the parliament to help tackle sexual harassment.

A Scottish Conservative party spokesman said: “Unfortunately, James Dornan has form when it comes to making crass and offensive remarks.

“Frankly, this is unbecoming of a member of the Scottish Parliament.”

Mr Dornan declined to say anything beyond his apologies on Twitter.

An SNP spokesperson said: "James has recognised that his use of language was ill-judged, and has issued an apology for any offence caused.”