The TV duo have admitted that after a few pints in their local they ended up locking horns - hours before appearing on TV.
Writing in their new book, Once Upon a Tyne: Our story, Britain's Got Talent star Ant says: "It was a special summer holiday version of the ITV breakfast show, in 1995, we were promoting Stuck On U.
"Our tour manager Kim Glover told us we had the day to ourselves before appearing on GMTV the following morning... so we went to the pub."
As Dec headed to the lift, Ant recalls saying: "What the hell are you going to bed for?”
Explaining how seeing Dec continue to "stumble towards the lift," Ant said that "something about that incensed me and I lost it".
Seeing red, Ant fumed: "Don’t you dare walk away from me when I’m talking to you."
Adding his version of events to the tale, Dec added how he started ranting at Ant, asking "who the hell does he think he was, talking to me like that?"
As they entered the lift arguing, Dec put his fingers in his ears to block out Ant's moans.
Admitting that was the final straw Ant admitted: "That made my blood boil… I punched Dec in the chest."
While he swung back, Dec said didn't cause any harm.
"I didn’t quite hit the target and ended up just punching the peak of his cap," he penned, prompting Ant to quip: "I proved Dec is rubbish at fighting when he’s had a few."
Once Upon a Tyne: Our Story Celebrating 30 Years Together On Telly is on sale now