Mr Bruce had chastised the Justice Secretary, saying: “Do you think  it’s appropriate for a Scottish Government Minister to talk in such a derogatory way about Scotland’s only indigenous lager brand of note?

“A lager brand that supports hundreds of jobs. One that has arguably been instrumental in creating a modern cultural landscape our country can be proud of. A brand which has been the longest running commercial supporter of football in this country, a sport I know you are personally very passionate about.

“And last but not least, a brand that is happy to donate the rights of the Scotland Under 21 teams.

“Bearing this in mind, do you think that your comment was appropriate? Helpful? Did it add anything to your message about responsible drinking?

“It is a shame it’s about you being at best flippant, at worst derogatory, about a brand which is committed to helping you and your Government tackle our nation’s drinking problem.”

Mr MacAskill, who made the remarks in March, was shamed into making a grovelling e-mailed apology by the tirade.

He wrote: “Rob, what did I say. It is my drink of choice and, if I said something inadvertently, then I unreservedly apologise. I don’t need persuaded of what you guys do so happy to try and set the record straight.”

He added: “It was meant as a whimsical aside and reference to higher ABV continental drinks that I now don’t touch.

“I accept it was out of order, so sorry once again. It was actually meant to be supportive though misplaced. Happy to sup a pint for you.

“Is that a fair offer of recompense. I have imbibed malts for the SWA and happy to be seen with your product as that’s what I consume in Leslie’s Bar.”

Mr Bruce accepted the apology and suggested meeting for “a pie and a pint”.

Mr MacAskill has taken a hard stance on binge drinking and has suggested Scotland’s inter-national football matches be played at an earlier time.

He also thinks minimum prices should be imposed on alcohol in supermarkets.