North Southwark and Bermondsey MP Simon Hughes told The Sun: "I have had both homosexual and heterosexual relationships".
Mr Hughes told the paper: "I hope that does not disqualify me from doing a good job in public life and I propose to carry on doing that with the usual enthusiasm and determination."
When asked last week by The Independent whether he was gay, the MP said: "The answer is no, as it happens. But if it was the case, which it isn't, I hope that it wouldn't become an issue."
Hughes now admits that those comments were "a mistake" and "overly defensive".
Earlier this week Hughes said that he regretted some elements of the Liberal campaign in the notorious 1982 Southwark and Bermondsey by-election, widely thought to have played on Labour candidate Peter Tatchell's homosexuality.
"hope that there will never be that sort of campaign again," he told Newsnight. "I have never been comfortable about the whole of that campaign, as Peter knows, and I said that to him in the past... Where there were things that were inappropriate or wrong, I apologise for that."
Mr Tatchell, now a Green Party supporter, is charitable: "Simon Hughes is the best of the Lib Dem leadership candidates. If I was a party member, he'd get my vote."