Simon Hughes will formally open his campaign for Britain's Liberal Democrat party leadership today.
Mr Hughes said yesterday he had had homosexual relationships after twice having denied to newspapers that he was gay.
"I am perfectly willing to say that I have had both homosexual and heterosexual relationships in the past," party president Mr Hughes (54) told the Sunyesterday.
"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."
In an interview with BBC radio last night Mr Hughes said he was sorry for his previous denials.
Mr Hughes will begin his campaign at the City of Manchester stadium. He is likely to stress his experience, vision and ability to campaign.
Mr Hughes, who is single, said he considered withdrawing his party leadership bid but decided to remain in the race and is competing against foreign affairs spokesman Menzies Campbell and economics spokesman Chris Huhne.
Mr Campbell (64), considered a safe pair of hands, is the bookies' favourite.
At the weekend, Mark Oaten, a married one-time leadership candidate, quit as Liberal Democrat home affairs spokesman after revelations of a relationship with a male prostitute.
Earlier in January, party leader Charles Kennedy was forced to resign after admitting a drinking problem he had previously denied.