Liam Gallagher has taken a swipe at brother Noel after he performed with two of their old Blur rivals, Damon Albarn and Graham Coxon.
The Beady Eye singer even said playing with their former enemies was as bad as his big brother meeting Tony Blair at Downing Street in 1997, reported the Daily Star.
Liam, 40, was winding up Noel, 45, over a performance he had organised for the Teenage Cancer Trust.
He tweeted: "Don't know what's worse RKID sipping champagne with a war criminal or them backing vocals you've just done for BLUE! LG x"
It is believed 'Blue' is a reference to Damon and Graham's band Blur, who Noel joined up with at the gig at London's Royal Albert Hall on Saturday.
Liam wasn't the only person surprised to see Noel performing with Blur, as the bands had a fierce rivalry during their Britpop heyday.
Former Oasis stars Liam and Noel have not spoken to each other since Liam quit the band in 2009.
Last Christmas Noel did extend an olive branch at the insistence of the boys' mum Peggy, by sending Liam a text.
But Liam replied with the put down "Who's this?" which Noel reckons he found "genuinely hilarious".