KT Tunstall has said she had reservations about appearing on TV to search for her biological father as she feared producers were after “a salacious, crazy, Jeremy Kyle-style nightmare scenario”.

The singer, who grew up in St Andrews, Scotland, has always known she was adopted and had tracked down her birth mother herself in 1998.

But when approached by ITV’s Long Lost Family series to help her find her biological father John, she said having “not watched telly since about the year 2000”, she was not sure what the programme involved.

She said: “I was totally not aware, really, of many programmes that are… these kinds of real-life programmes. And obviously the worry is, what’s the agenda here? Are they wanting some sort of salacious, crazy, Jeremy Kyle-style nightmare scenario that is going to get everyone watching?

“It became absolutely apparent very quickly that this was a very emotionally mature, very experienced team who literally just want to find family members, put them together in the safest and most positive possible way. So that was sorted out really quickly and after I realised that it was like, ‘Yeah, no-brainer’.”

She is the first celebrity to appear on the show and the 44-year-old also discovered she has two half-sisters – Siobhan and Lesley-Anne.

In addition, her birth mother, Carol Ann, had given her some information on her father.

But a reunion was not meant to be as during the search Tunstall was told off camera that John had died in 2002.

She said: “I knew his name, I knew that he was Northern Irish, I knew that he ended up living in northern Scotland. And then when I met my biological mother, she told me a bit more about him as well.

“But she’s always said that he’s a good person, with a good heart. He’s a nice guy. She told me straight off the bat that he wanted to get married and keep me and be my father, but she was just not able to do that in her life, with him.”

Of her newly found siblings, she said: “I think our father had found it very difficult that he wasn’t able to bring me up and be my father and I think there was some guilt and shame associated with that, so he obviously made the decision to not tell his family about it.

“But when I met my biological mum, the two things that I was really interested in is, do I look like her? And where does my musicianship come from, because that’s not something that I share with my adopted family.

“And pretty much the first thing she said to me was, ‘Oh my God, you wouldn’t be able to walk past your dad on the street – and he was an amazing singer’.”

Tunstall will perform at Glastonbury and is also heading to Japan and China.

The Suddenly I See singer said penning happy songs is more difficult than writing depressing ones.

She added: “I don’t write very much when I’m on tour, it’s kind of all-consuming for me on tour. But I have been known to write stuff down in journals sometimes.

“But I’m making a new record this autumn and it’s the final in a trilogy of records about soul, body and mind. I’ve done the soul one and the body one, and the mind one will be out next year hopefully!”

KT Tunstall appears on Long Lost Family on ITV on Monday July 1.