The comedian, 34, and his father Michael, 83 – who he has featured on numerous shows with – appeared on The Chris and Rosie Ramsey Show on Friday.
Co-host Rosie told the pair: ‘You two come across like you’ve got a lovely relationship.’
Jack then replied: ‘Behind closed doors we’re like Holly and Phil. We don’t speak to each other.’
The joke prompted gasps from the audience with Jack then saying: ‘What? Come on.’
Jibe: Jack Whitehall left a chat show audience gasping as he made a dig at Holly Willoughby and Phillip Schofield amid their ongoing feud
Feud: Jack said of his relationship with his father: ‘Behind closed doors we’re like Holly and Phil. We don’t speak to each other’
Reaction: The joke prompted gasps from the audience while Rosie looked playfully shocked
Rosie also looked playfully shocked by the jibe while Chris laughed.
It comes amid reports that the This Morning co-hosts are ‘not as close as they once were’ and now barely speak off-camera.
As the feud continues to rumble on with no sign of the presenters stepping down, it has been revealed that the rift may actually have started three years ago, when Holly began to ‘quietly distance’ herself from her longtime friend.
It’s also thought that Phillip was irked when Holly landed a job filling in for Ant McPartlin as the host of I’m A Celebrity Get Me Out Of Here! in 2018.
Holly, 42, and Phillip, 61, plan to take a week off for the half-term break, before returning to the programme on Monday, June 5, according to The Sun.
The Daily Mail has also exclusively revealed that Holly has now lined up Alison Hammond as a replacement for Philip – with ITV thought to be in agreement.
The now tense relationship between the pair reportedly first began over their celebrity talent management agencies.
The co-stars were once part of the same management – YMU Group – before Holly split from them to start her own agency Roxy Management.
More tension: The feud between Holly Willoughby and Phillip Schofield is now thought to have begun three years ago (pictured on This Morning on Thursday)
However, her tie to her old management became a fraught one as they became embroiled in a legal battle over her future earnings.
The case was settled out of court, with Holly earning £1million from them.
Phillip on the other hand has chosen to stick with them and is even a shareholder – starting a series of divisions between the two.
According to The Sun, he is said to earn £1million from them and is a ‘big player’ in the group.
A source told the newspaper: ‘Holly quietly started to distance herself from Phil back in 2020. The legal issues rumbled on for 18 months but Holly fought for what was right.
‘Ultimately, Phil chose to stay and Holly chose to leave, it wasn’t easy at the time.’
MailOnline has contacted representatives for Holly Willoughby and Phillip Schofield for comment.
Time off: Holly, 42, and Phillip, 61, planning to take a week off for the half-term break, before returning to the programme on Monday June 5, according to reports
Earlier, in 2018, Phillip was widely known to be ‘annoyed’ after Holly was chosen to step in for Ant McPartlin to co-host I’m A Celebrity… Get Me Out Of Here with Declan Donnelly.
While continuing to present This Morning with no Holly, Phillip admitted he wished he was also hosting the jungle show.
This only increased Holly’s success as a break-out star away from her former best friend Phil.
She became the presenter of Take Off With Bradley & Holly on BBC1 and launched her own lifestyle brand Wylde Moon in 2021.
Profitable collaborations followed for the presenter, including with Marks and Spencer, which is thought to have earned her £950,000.
Phil has tried to launch his own side projects – such as gameshow The Cube on ITV – but they have time and time again failed to get off the ground.
Following the Queuegate scandal – which further emphasised the rift in their friendship – Phillip was dropped from his deal with WeBuyAnyCar.
Previously, the first signs of a falling out were thought to have begun in September, when the pair were criticised after failing to queue for the Queen’s Lying in State.
Replacement: It’s now understood that Holly wants Phil to leave and for Alison Hammond (pictured) to step in
Phillip is thought to harbour jealousy for his co-star as he was the bigger name when they first began working together in 2009.
Meanwhile, leading bookmakers have revealed the odds of both Holly and Phillip being replaced on This Morning.
Irish bookmaker Paddy Power revealed the chances on Phillip exiting This Morning, putting him at 2/1, while they placed his co-host Holly at 4/1 odds.
Meanwhile, William Hill made it 4/1 odds that Holly could leave This Morning before June, also putting her at 6/1 odds that she could take up a new job on Loose Women.
She is at 10/1 to be given hosting duties on Strictly Come Dancing and the bookmaker also predicted 20/1 odds for her to present I’m A Celebrity.
William Hill spokesperson Lee Phelps said: ‘There seems to be plenty to suggest that Holly Willoughby’s time on This Morning might be coming to an end and we offer 4/1 that she departs her role by the end of the month.
‘Holly will surely be hot property if she does depart and we think the likes of Love Island and Loose Women (both 6/1) and Strictly (10/1) will be on the agenda.’