The First Minister has laughed off questions about whether or not he smiled at Hampden when fans loudly booed God Save The King. 

READ MORE: Ally McCoist brands Scotland fans 'out of order' for England booing

Footage of Humza Yousaf apparently "smirking" as the Tartan Army drowned out the national anthem being played for England was obtained by the Scottish Sun.

The video showed the SNP leader seemingly stifling a smile as he stood alongside the SFA's chief executive Ian Maxwell ahead of Tuesday's  150th Anniversary Heritage match between Scotland and England.

The onlooker who shot the film told the paper: "He appeared to be smirking throughout the national anthem. It wasn't really how you would have expected him to react to the booing. The sensible thing would have been to maintain a stony-faced demeanour throughout, in a dignified manner."

Conservative MSP Murdo Fraser said: "Humza Yousaf has made no secret of the fact that he's a Republican but, as First Minister, he has a duty to show respect to our Head of State and all nations and anthems. He fell short of that."

Speaking to journalists during a by-election campaign stop in Rutherglen and Hamilton West, the First Minister was asked directly if he had smirked while fans booed. 

"Ha," he said. "Smirkgate. This is the best question I've ever been asked."

He continued: "You can ask me about all of government policy and you're asking me whether I was smiling at the football game?"

"I may have been smiling at the football game, and Steve Clarke has given us plenty to smile about," he added.

Asked if he thought England should adopt their own national anthem rather than use God Save The King, the First Minister said, "I've never been one to tell the people of England what to do, and I certainly don't intend to start now."

READ MORE: Jude Bellingham says anthem booing spurred England on for Scotland win

He was also asked about Flower of Scotland. There has long been debate over the song. Recently, ex-Scotland rugby coach Jim Telfer called for it to be replaced. 

Mr Yousaf said: "I love Flower of Scotland. I enjoy it as an anthem.

"Maybe it's because I've been going to Scotland games all my life and enjoy the Hamden Roar and the whole of Hampden as we saw earlier this week, coming together to belt out  Flower of Scotland so I do enjoy it."