Users on social media were quick to poke fun at the incident – first spotted and reported by the News Letter – which happened during a segment by the actor and comedian Doc Brown, who was performing a spoken word poem celebrating UK sport.
A BBC spokesperson said: “The incorrect flag appeared in a brief montage during Doc Brown’s appearance last night. We apologise for the error and the sequence will be edited on iPlayer.”
As the comedian was speaking, images were projected on the screen behind him, including an England and Wales football badge, a Scottish flag and the Irish tricolour, as the performer referred to the “three lions” and then added: “Same with the red dragon, shamrock and thistle.”
“Sport is the leveler, now to the finish, son of an immigrant proud to be British,” he continued.
The moment seemed to cause confusion among some online, as others laughed at what they considered a mistake by those behind the star-studded concert.
Twitter user Demot O’Callaghan wrote: “What’s that about, tricolour. Since when are we British?
Catherine Kelliher added: “Dear organisers of today's event, I really enjoyed the Platinum Party but the Irish tricolour shouldn't have been used to represent the UK.”
Terry Brennan asked: “@BBCOne did you just include the Irish tricolour in a song about being ‘proud to be British’?”
Another person wrote: “Did they really use the Irish tricolour to represent N. Ireland at the #PlatinumPartyatthePalace.”
Commenting on the flag-based faux pas, the DUP MP Gregory Campbell said: “The Platinum Party at the Palace was a part of what will be regarded as an outstandingly successful recognition of Her Majesty's 70 years as the Monarch.
"It was unfortunate that in a very short video clip during the event when the four Nations that make up the United Kingdom were visually represented by logos or flags that the Irish Tricolour was used instead of the Ulster Banner.
"Hopefully those responsible will have realised their mistake and will ensure that in the event of any future occasion where the four Countries of the UK are to be visually represented, more care is taken to ensure a mistake like this one is not repeated.“
The TUV leader Jim Allister added: “Quite an appalling and wholly disrespectful blunder which contrasts with the professionalism of the range of Jubilee events. The lack of oversight, which permitted such a fundamental affront to this part of the UK, requires both explanation and apology.”
The concert in front of the Royal Family, including Prince Charles and Prince William, saw dozens of artists take to the stage to wow the tens of thousands watching live and the millions tuning in at home.
Queen and Adam Lambert delivered the stunning opening to the concert, with Rod Stewart, Diana Ross, Duran Duran, Mabel and George Ezra just some of those playing their hits to mark the Queen’s 70 years on the throne.