Former Oasis star Liam Gallagher is taking legal action against his brother Noel for what he claims are "lies".
The singer has been enraged by comments made by his guitarist brother last month in which he alleged Liam pulled out of a major festival appearance because of a hangover.
He also disputes Noel's story about how the seeds of Oasis's split were fuelled by a row over plugging Liam's clothing range Pretty Green during the band's tour.
Now the frontman - who has relaunched his music career with Beady Eye - has issued a High Court writ against his brother.
He made the extraordinary move because he said he wanted Oasis fans and festival-goers "to know the truth".
Noel walked out on Oasis following a row moments before a festival in Paris two years ago.
He opened up about the decision to leave at a press conference in London last month.
The musician - who also wrote most of the group's hits - said the Gallaghers' rocky relationship worsened after Liam demanded free plugs for his clothes brand in the tour programme, which Noel opposed.
He also said Liam pulled out of an appearance at the V Festival in Chelmsford in 2009. At the time it had been explained as a bout of laryngitis, but Noel said the reason for the no-show was his brother's "hangover".
In a statement today, Liam confirmed his legal action and said he was looking for an apology to put the record straight about the festival cancellation.
He said: "That is a lie and I want Oasis fans, and others who were at V, to know the truth.
"I was gutted when I couldn't play the gig because I didn't want to let the fans down."
The duo have had a long-running public spat ever since they found fame in the mid-1990s.
Cancellation of a major festival appearance due to a hangover rather than a medical condition could potentially lead to contractual issues with the organisers.
But Liam's statement said it was laryngitis "diagnosed by a doctor" that stopped him performing.
Liam also dismissed the suggestions of an argument about his fashion line.
"There are many reasons why Oasis split. But it had nothing to do with my clothing range," he said.
The 38-year-old - who started his latest band with the remaining members of Oasis - pointed out that there had been many slanging matches between the pair.
But he added: "What Noel has alleged this time went way beyond rock-and-roll banter and questioned my professionalism."
Liam said the legal response had come about because efforts to solve the issue "amicably" had failed.
"This is not about money, all I want is a full apology from Noel," he said.
Noel's representatives did not want to comment about the legal action.