Mark Oaten, the one-time Liberal Democrat rising star who left politics 13 years ago after it emerged that he had been regularly paying male sex workers while married, has said he is now gay, and living with another man.

The former Lib Dem home affairs spokesman and MP for Winchester, who was standing to become the party’s leader until just before the revelations in 2006, said it had taken him until now to go public with his sexuality.

“I’m gay now, and I’m comfortable with being gay and I’m clear about my sexuality,” he told BBC Radio 5 Live.

“I haven’t actually said it until now in an interview. It’s something which is difficult for me to say. It still feels difficult for me to say, but increasingly I’m comfortable and happy about that, and feel in a comfortable place to say that to you today.

“But it’s been a long journey to get me to that point. I clearly had sexual doubts earlier on in my life, but I was very, very happily married and really, really enjoyed being a dad and married as well.”

Oaten was married with two daughters when the News of the World published details about his six-month relationship with a male sex worker, and how he had paid to take part in group sex sessions.

The former PR consultant was only 33 when he became an MP in 1997, and made his name as the voice of so-called “tough liberalism” in the home affairs brief, moving the party to the right on immigration and crime.

He stood to succeed Charles Kennedy when the then leader announced in January 2006 he was stepping down due to alcoholism, and was Kennedy’s choice for the post. Oaten dropped out of the race shortly before the newspaper revelations because of what he said was a lack of support for his bid.

He quit parliament in 2010, and stayed with his wife Belinda. Oaten said his family had been supportive of his later change in lifestyle.

“It’s something my friends have known about now, my girls know about, and my mum – those key people – but it’s only been in the last year, year-and-a-half. I’ve got a partner, we live together. I have a group of great gay friends. I can be who I am now. I just wish I’d done it earlier.”

Oaten said his use of sex workers had been in part a reaction to life in the “seedy, bullying men’s club” of parliament.

He said: “You are in an environment where you can buy drink really cheap, you are in an environment where you are away from home and your family, and you are in this kind of bubble where you are able to get away with anything you want. You are conscious and aware of colleagues having affairs.”

Oaten, who left the Lib Dems last year, said he felt Vince Cable should step down as leader. “He’s failed and the party’s failed. I think Jo Swinson is good and great. I think frankly, Vince, it’s time for you to step down and let somebody new come through.”

Oaten’s political career began amid some drama – in 1997 he won Winchester from the Conservative incumbent, Gerry Malone, by just two votes. Malone challenged the result in the courts and forced a byelection, which Oaten then won with a majority of 21,556.