Steven Broomhead, 42, claimed the relationship began when a normal “kiss and cuddle” with Chelsea Cummins, then 18, developed into something more serious.
During their secret relationship Cummins, who represented Britain at tae-kwon-do, became pregnant and had an abortion.
The affair was exposed when Broomhead rekindled a romance with her mother, Lisa Cummins, prompting Chelsea to warn her of his behaviour.
Mrs Cummins assumed her daughter had been raped and informed police, who discovered the truth about the affair.
At Minshull Street Crown Court in Manchester both Cummins and her father walked free after they were convicted of sexual offences.
Rachel Shenton, prosecuting, said: “Chelsea Cummins was…Steven Broomhead’s natural daughter. She did not grow up knowing him as her father and was adopted by her step-father at a young age.
“She got back in touch with the defendant when she was 17. Neither can agree on how they started their relationship.
“Chelsea Cummins alleges that she was in fear of her father. Steven Broomhead gave a different account in which he says that his daughter was the instigator and a normal kiss and cuddle became something more and she was the one in control of the relationship.
“This became a mutual relationship in which they had sexual intercourse on a number of occasions at the defendant Steven Broomhead’s home and also his place of work.”
Miss Shenton said Cummins became pregnant in 2006 when she also had a boyfriend.
“She did not know if the father was her boyfriend or the defendant Steven Broomhead.
“And that formed part of her decision to have an abortion…
“The relationship continued after the end of her relationship with her boyfriend and she moved in with her father until April 2007 when she moved back to live with her mother.”
The court heard that Cummins became jealous after discovering Broomhead had another lover called Lisa.
She realised Lisa’s identity when she saw them together.
“She was living with her mother and she told the police that she had walked in on Steven Broomhead on top of her mother.
“Matters came out when the mother had been out drinking with Steven Broomhead and when she got home Chelsea said to her mother ‘He’ll only cheat on you.’”
Although Cummins, from Denton, said the relationship had been consensual her mother reported Broomhead, also from Denton, to police.
During the investigation Cummins told officers: “He has never been my dad and so I didn’t look at him like that. I did have sexual feelings for him – it wasn’t planned and I didn’t think about it after because it just happened.”
Defending Cummins, Gary Woodall said: “Chelsea Cummins found herself turning to her father at 17 years of age in an emotional state after becoming estranged from her mother, not having known her father until that age…
“She is now 21 years of age and of good character. Her educational background shows that she has obtained qualifications and you will see that she has represented this country in the world championships in Korea and Egypt in her chosen sport.”
Cummins admitted two counts of sexual activity with an adult relation and was given an absolute discharge.
Judge Andrew Lowcock told her: “In my view you were very much not in control of what took place. You were an extremely confused young woman and it is clear that you are a young woman with a lot of potential and I hope that you put this matter behind you.”
Sentencing Broomhead to three years supervision and ordering him to attend a sex offenders programme, Judge Lowcock said: “(Cummins) said she knew it wasn’t right but there was a power differential between you – you were her father and you were responsible for her.
“She trusted you and you abused that trust. You seem unable to accept your responsibilty and put the blame on your daughter.”