Comedian Seann Walsh has insisted he's "not the person I'm being portrayed as" after being caught kissing his Strictly Come Dancing dance partner Katya Jones.
They were photographed together on a night out, leading Walsh's girlfriend to end their relationship.
The pair apologised during an appearance on BBC Two's Strictly - It Takes Two on Wednesday.
An emotional Walsh said: "I made a mistake, which I'm very sorry for - sorry for the hurt that I've caused."
He and Jones, the winner of last year's Strictly, had previously apologised on Twitter after their public kiss came to light.
Speaking on It Takes Two, Walsh said: "You never think about the extent of the damage that you're going to do in a moment of... you know, the mistake that you've made.
"I'm not perfect, far from it. Our relationship wasn't perfect. That doesn't mean I wanted it to end the way it finally did, and I'm very sorry for that.
"I feel it's also important for me to say that the people that know me the most, that love me, they know that I am not the person I'm being portrayed as. I'm still sorry for what I did, but it's very important for me to get that out there."
Walsh's ex-girlfriend, actress Rebecca Humphries, has accused him of "controlling" behaviour.
In her Twitter statement announcing she was leaving him, she said he "aggressively, and repeatedly, called me a psycho/nuts/mental" when she voiced suspicions.
Jones, 29, who is married to Strictly professional Neil Jones, told the programme: "I can't apologise enough to everyone who it hurt and involved.
"But, the main thing, me and Neil are absolutely fine and that's what matters to me the most right now and focusing on my job and doing it as professionally I can."
Despite the controversy, the pair are continuing in the BBC One dance competition.
A list of songs and dances announced on Tuesday revealed Walsh and Jones are set to perform a Charleston on Saturday's show to Bills by LunchMoney Lewis.
It had been reported that they were originally set to do a rumba - but have had their routine changed to something "less sexy".
Walsh, 32, said the kiss happened after they had had a couple of drinks. "We were getting on well, we were having fun," he said.
It's the latest - and most public - example of the so-called Strictly curse, which has been blamed for a number of relationship break-ups over the years after contestants have become close to their professional dance partners.