Strictly fans were left aghast when images came to light showing the couple enjoying a steamy kiss in the street following a boozy, post-training night out and on Seann's ex-girlfriend Rebecca's birthday, where she waited at home alone.
Reflecting on his separation, he added: 'I made a mistake, which I'm very sorry for - sorry for the hurt that I've caused.
Katya's husband, fellow Strictly professional Neil Jones, has admitted he never feared his missus being caught up in the "Strictly curse".
A Strictly source said to The Mirror: "Seann spent most of Saturday in his dressing room or quiet corners away from the other celebs in the run-up to filming the main show and the results show".
"I feel sorry for them", she said.
Some viewers of the Saturday night show had been outraged to see Seann his usual chirpy self after a strongly-worded open letter from ex Rebecca, which accused him of treating her terribly throughout their relationship.
Seann, meanwhile, was dating long-term girlfriend Rebecca Humphries, but he has since been dumped following the leaked kissing photos.
"In light of the story in today's newspaper I would like to offer my honest apologies for my actions, ' Seann's statement read on Sunday, "This is no excuse but it was a one-off drunken mistake which I am truly sorry for.' Katya's reiterated the drunken mistake, stating that the 'one-off mistake after some drinks" was 'not a reflection" on her five-year marriage to fellow professional dancer Neil Jones- who has also previously appeared on Strictly Come Dancing.
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Rebecca also labeled "controlling" and said she had taken their cat.
In a Twitter post, Ms Humphries wrote: It's incredibly good of Sean (n) and Katya to apologise in the media.
"But I have had a great experience you know and I feel really privileged to have been here and thanks for your advice and thank you Gorka for all the hours!"
"I don't think it's making people go right well everyone's doing, it we can have an affair".
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. "It's controlling. Tell some very close friends who, if they're anything like my wonderful network, will swoop in and take care of the logistics and you".
Humphries statement comes as Walsh and Jones have cancelled a slew of planned joint publicity commitments for their Strictly Come Dancing stint - amid calls for them both to be axed from the show.
"Believe in yourself and your instincts".
She finished by stating that she was now "free" and that she hoped Seann "gets what he wants from this".