Stephen Flynn has been criticised for seemingly not singing the national anthem at the Remembrance Day memorial service at the Cenotaph today.
Scottish Conservative deputy leader Meghan Gallagher claimed the SNP's Westminster leader had "fallen shamefully short".
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She said: "Stephen Flynn is entitled to his republican views, but as Westminster leader of the SNP he has a duty to show respect to our head of state and to all nations and anthems.
"By apparently refusing to join in with the national anthem, especially at a service to honour those who gave their lives for this country, he has fallen shamefully short of this."
But writing on X after the ceremony, Flynn said: "A humbling experience to be present at the Cenotaph today for Remembrance Sunday, and to lay a wreath on behalf of the SNP and Plaid Cymru.
"As ever, I was thinking of my late grandad and the sacrifices his generation made during WW2 to protect our freedoms. Lest we forget."
An SNP spokesperson told GB News: "Stephen Flynn was honoured to represent the SNP at the Service of Remembrance at the Cenotaph, which is about remembering the sacrifice of all those that have defended our freedoms, including members of Mr Flynn's family.
"It is disappointing that the Scottish Conservative Party is seeking to politicise Remembrance Sunday in this way, on a day when we should be united in remembering the service of others."
The party hit out at claims that Flynn hadn't been singing, describing Gallacher's comments as "grotesque".
A two-minute silence was observed at 11am today.
As many as 10,000 veterans and armed forced personnel took part in the ceremony, which was also attended by Prime Minister Rishi Sunak and Labour leader Sir Keir Starmer.
Remembrance weekend was bound up in controversy and unrest as both pro-Palestine and right wing protesters descended on London.
Police were forced to use batons to hit back protesters as they breached police lines, while hundreds of screaming Britons were heard chanting "England 'til I die".
A number of arrests were made and several members of the police were left injured.
This came just one day after Suella Braverman penned an Op-Ed in the Times, accusing the Met Police for "playing favourites" when it comes to the policing of protests.
She said the pro-Palestinian marches are "problematic" because of "violence around the fringes", in addition to "highly offensive" chants, posters and stickers.
Some blamed Braverman for the weekend's violence, claiming the remarks have stoked up tensions in Britain.
Baroness Warsi, a Conservative peer, said the Home Secretary "had lit the touch paper and ignited community tensions" with her remarks.
She told the Evening Standard: "Couching the planned demonstration as 'armistice day vs a hate march,' she has pitched community against community and set a noisy call for peace against a quiet moment of reflection to mark the war."
But Tory MP Brendan Clarke-Smith dismissed those blaming Braverman for the disruption as "daft", adding: "These protests have been going on for weeks and this clash with Armistice Day had been scheduled for a while.
Suella Braverman penned an Op-Ed in the Times, accusing the Met Police for "playing favourites" when it comes to the policing of protests
"If anything it shows she was right."
Fellow Tory MP Jonathan Gullis hit out at the protesters, dismissing them as "deeply unpatriotic".
Writing on X, he said: "These acts of thuggery are completely unacceptable and deeply unpatriotic.
"All this mindless yobbery does is undermine the overwhelming law-abiding majority of British people who want this weekend to remain sacred and solemn, so as a nation we can remember our glorious dead."