The Beady Eye singer is said to have fallen for his former personal assistant Debbie Gwyther, and sees no hope for his current marriage.
"Liam has known Debbie for a while and really, really adores her," a close friend of the singer told The Mirror. "He knows that she is the woman he wants to be with, not Nicole or Liza. So that's it for his marriage."
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Liam and Nicole's marriage hit the rocks when reports emerged in July that the former Oasis frontman had allegedly fathered a love child with New York Times journalist Liza Ghorbani.
"He has looked into the first stage of divorce proceedings and takes the view that there is no point hanging around and not doing anything," added the source. "They may as well get on with it and move on with their lives."
The hope that Liam and Nicole may be getting back together was suggested when the former All Saints singer was spotted out for dinner just three days ago, with her wedding ring back on.
The couple have one son together, 12-year-old Gene, and are said to be in telephone contact to discuss how the situation will affect him.
"Liam phoned her the day before it came out and he hasn't been in touch since," said Mary, Nicole's mother. "She can't get hold of him. She's absolutely devastated. This is so out of character for the Liam I know."
Nicole was on holiday in the US with her family when she was told, while Liam remained in Ibiza to perform with his band. He was pictured with her former personal assistant Debbie, who he is said to have been dating for months.