Michael Gove hit an ace back at Alex Salmond's Saltire photobomb, saying Scotland's First Minister should "Put it away dear".
Barely concealing his glee, the Education Secretary suggested it was inappropriate behaviour for Wimbledon's Royal Box, telling Nick Ferrari on LBC 97.3: "I think there is a difference between how you might behave in the Royal Box in Wimbledon and how you might behave in Hampden if a Scottish football team were to win.
"I think it was a wee bit of a stunt... my advice to Alex would just be 'Put it away dear'.'"
Cameron's official spokesman declined to say whether the Prime Minister regarded the First Minister's action as a "stunt", telling reporters: "You will have to ask Mr Salmond about that."
He added: "What the Prime Minister did was to ask for the Saltire to fly from Downing Street yesterday."
The blue-and-white flag of St Andrew was raised over Number 10 before the match began on Sunday.
Asked whether Cameron was celebrating Murray "as a Scot or as a Brit", the spokesman said: "The two go hand in hand, and the Government's approach to the independence campaign in Scotland is that that should continue."
The SNP leader seemed to deliberately raise the flag behind the Prime Minister's head in the Royal Box on Centre Court yesterday so it would be in the television shot.
Supporters of the Union have accused him of "photo-bombing" Cameron and breaking All England Club rules - which state that large banners and flags cannot be used around the courts.
Salmond told the BBC Radio 4 Today programme that he had "no idea" what the seating plans were, and the Wimbledon authorities had not minded his actions "in the slightest".
"I think it (is) a rule more observed in the breaking than the observation," he added.