The 'Strip That Down' hitmaker was convinced the former Girls Aloud singer - the mother of his 14-month-old son Bear - was ''going to kill'' him after he asked her during his live interview with Nick Grimshaw on his 'Breakfast Show' this morning whether she had been doing a ''number one or number two'' when he called for her.
The embarrassing moment unfolded when Nick asked the 24-year-old singer who had the biggest entourage between him and the 'Call My Name' hitmaker.
Completely puzzled by the question, Liam - who was doing the interview from home over the telephone - went in search of the 34-year-old former television judge.
He then stopped in his tracks and said: ''She's actually in the toilet.''
But that didn't stop the former One Direction star from trying to get her attention as he called through the bathroom door: ''Cheryl? Can I ask you a question?''
As she opened the door, he queried: ''First off, was it number one or number two?''
The brunette beauty, clearly unamused to be quizzed about her possible bowel movements on live radio, screeched in the background: ''Stop it!''
Liam joked: ''She's going to kill me after this. Hopefully I'll survive the wrath of the Chez.''
This isn't the first time Liam has embarrassed Cheryl in public as he previously revealed he calls her ''old Cheryl'' - due to their 10-year gap - and would happily give her away in exchange for a tasty In-And-Out burger if he had to choose between the two.
Despite Cheryl trying to keep her private life out of the limelight, Liam also recently revealed that not ''everything is absolutely fine and dandy'' all the time.
His new album Underneath It All is out now.
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