Sara originally hit out at the 46-year-old rocker - who has been in a bitter feud with brother Noel since their band Oasis split in 2009 - in a now-deleted Instagram post in which she said she wouldn't be watching Liam, whom she described as a ''fat t**t'', performing at Glastonbury in June.
She wrote: ''Think I'm going to swerve that. The fat t**t doing his tribute act balancing a tambourine on his head is going to look pretty dated after Stormzy.''
Days later, 52-year-old Noel accused his estranged sibling of sending threats to his family, when he shared a screenshot of a text message that Liam had allegedly sent to Noel's 19-year-old daughter Anaïs, asking her to tell her stepmother to be ''very careful'' in the wake of her comments.
Alongside the screenshot, the 'Black Star Dancing' singer wrote: So you're sending threatening messages via my teenage daughter now are you? You always were good at intimidating women though, eh? What you planning on doing anyway? Grabbing my wife by the throat to show her who's boss ... or maybe trying to waddle through our double gates and performing ''S**twave'' in the communal garden or daubing your w**k lyrics on the toilet walls? If I wake up to find one of the kids gerbils upside down on the cheese board with a knife in it I'll sure to inform the local care in the community officer. And don't try and kidnap the cat either we've just employed Ross Kemp as his close protection officer. Enjoy the summer big t*ts. Catch up soon. (sic)''
Now, Liam has insisted he didn't threaten Sara, and although he has apologised for getting his teenage niece involved, he didn't appreciate being called ''fat''.
Speaking to Mr Porter Journal, he said: ''He said I threatened his wife. I didn't threaten his wife. If you threaten someone you have to say, 'If you do this, this is gonna happen.' I probably shouldn't have brought Anaïs into it, and I apologise. [Noel's wife] called me fat, which hurt my feelings. I have a belly, it's well paid for, but I'm not fat. Then he [Noel] hung himself by slagging off Scotland. Good luck gigging in Scotland by the way, our kid.''
The 'Shockwave' singer had already apologised to Anaïs and his mother Peggy Gallagher for the text message, in a note posted to his Twitter account in July.
He wrote: ''My sincere apologies to my beautiful mum Peggy and my lovely niece Anais for getting caught up in all of this childish behaviour I love you both dearly LG x (sic)''
His new album Underneath It All is out now.