The 27-year-old model, who was seen insulting his potential partners in a disastrous display on last week's episode, had been secretly dating Sarah Ann Gras when he filmed his appearance in November.
Merry eventually won a date with a reluctant contestant named Chelsea Stewart, but tied the knot with Gras in Las Vegas early last month.
"I couldn't believe it when I saw him on the show," a friend told The Mirror. "He's been dating Sarah since long before the show was filmed, and they got married in Las Vegas earlier this year.
"I'm shocked at the things he said on the show. All that stuff about being unlucky in love is just nonsense. He's had plenty of girlfriends before Sarah, and been with her a good while before the show.
"I wouldn't be surprised if all of this was a stunt just to try and boost his modelling career by getting on the telly. It's the poor girl who had to go away on a date with him that I feel sorry for - he has totally wasted her time."
Merry, a former boyfriend of Jodie Marsh, has claimed that a friend assumed his identity and got married.
A Take Me Out spokesperson responded: "All contestants are required to confirm their single status during the initial phase of the application process and Damion repeatedly claimed to be single.
"We also carry out a number of background checks and speak to family members and close friends to research a contestant's background and find out more about the information they have provided. At no stage was it suggested that Damion had a girlfriend."
Speaking to The Sun's TV Biz, Stewart said that her date with Merry had been a nightmare from start to finish.
"He kept putting his foot in it. I didn't want to go, the way he'd acted," she said. "He was so arrogant. He tried to compliment me but realised he wasn't going to get anywhere."
The date will be shown in tonight's (February 11) episode of Take Me Out, which airs at 8pm on ITV1.
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Watch Damion Merry attempt to woo the Take Me Out girls below: