Long famed for their fisticuffs and slanging matches, the intense sibling rivalry between Liam and Noel Gallagher now includes allegations of plagiarism.
In an interview with Uncut magazine, Liam has said his estranged brother and former Oasis bandmate "swiped" the pair's old material for a new solo project, the details of which are still to be confirmed.
"I've heard his fucking new record 'cos I fucking sung on half of it," Liam said. "Fucking nonsense... it's all very hush-hush 'round his camp. I put up with 18 years of that fucker so I'm [not] arsed [with] what he's doing."
Alan McGee, who signed Oasis to Creation Records in the 1990s, has heard two of Noel's new tracks and backed Liam's claims. But Mr McGee also praised Noel's new material.
According to the former Oasis frontman, the tracks on his brother's new record were written during sessions in Los Angeles for Oasis's last album, released in 2008. "When I was in America for Dig Out Your Soul, he swiped some off because he obviously wanted to do a solo album," Liam said.
Oasis broke up in August 2009 after the brothers' backstage fight at the Rock en Seine festival near Paris. The fracas, which caused damage to one of Noel's guitars, resulted in the cancellation of both the gig and entire European tour.
A statement from Noel appeared on the band's website two hours after the argument. It stated: "With some sadness and great relief... I quit Oasis tonight. People will write and say what they like, but I simply could not go on working with Liam a day longer."
Noel played his first post-Oasis gigs at the Royal Albert Hall last March. Liam, meanwhile, formed the new band Beady Eye last year with Oasis's remaining members.
Liam also told Mojo magazine in a separate interview that he thought Noel's new record contained "songs for 50-year-olds".
He told the publication that Oasis fans should "let go of the Oasis dream", likening the situation to a soured love affair. "It's like wanting your girlfriend back after she's fucked you off. You'll end up getting yourself ill," he said.
"In my experience of Liam Gallagher, he does tell the truth," Mr McGee said of Liam's claims.
"But as far as the comment about 50-year-olds is concerned, I don't have a problem with it, because I'm 50. I am a fan of both Liam and Noel's music."
Mr McGee said Noel's new material sounded like Oasis circa their celebrated 1995 album, What's the Story Morning Glory?, which has sold an estimated 22 million copies worldwide. "The work sounds like the trademark generic template of Oasis," he said. "Minimalistic, but very anthemic, to be loved by someone 21-years old or 50-years old.
"As far as it sounding like Oasis, well, any band can sound like anything. Kraftwerk could release an acid house album. But if Liam's saying that then he must be telling the truth."
Liam also told Uncut he hadn't seen his brother since the group disbanded. "I haven't seen him," he said. "I'm not arsed with what he's doing. I'm sure it will all be very civilised and grown-up. His gigs will be like those that you can really stroke your chin at. With four rent-a-Scousers wearing shell suits."
Spokespersons for both Noel and Liam Gallagher refused to comment.