The denial comes after Peter reportedly sought legal action against his ex.
Katie, who is currently on a UK tour, is said to have compared the end of her and Peter’s marriage to BBC drama Doctor Foster during one of her candid onstage chats.
The show famously revolves around a woman whose husband has an affair with a much younger woman, and when a fan asked about Pete, Katie is said to have replied: “I don’t stalk anyone. Have you seen Dr Foster?
“That’s the answer to that question. Use your brain if you know what I’m trying to say.”
Shortly after the news broke, Katie tweeted: “I did not ever say in any words from my mouth on my tour to suggest Pete cheated on me as everyone knows he never did. Sorry. [sic]”
A source then claimed to The Sun that Peter was seeking legal advice over the defamatory comments and that is why she had apologised.
They explained: “Peter didn’t cheat on Katie and wasn’t happy when she suggested he had during her tour.
“After her comments were made public, Pete got his lawyers involved and Katie was issued with a legal letter.
“That’s the real reason she tweeted to say sorry.
“Pete never cheated on Katie. He never speaks about her and can’t understand why she just won’t leave him alone.
“She always brings him, or their marriage, up and he just wishes she would stop.”
Yahoo Celeb UK have contacted Katie and Peter’s reps for comment.