The co-chairman of the campaign to select Senator John McCain as the Republican US Presidential candidate has resigned after offering an undercover police officer $20 (£10) for oral sex.

Bob Allen, a Florida state representative who has voted against a range of gay rights measures, was spotted by police in Titusville, Florida on Wednesday acting suspiciously at the men’s toilets in a park.

Officers decided to send a policeman undercover to investigate, and within minutes Mr Allen had made his financial offer.

He was arrested and charged with solicitation to commit prostitution and faces a year in jail or a $500 fine.

“After he was arrested, he mentioned he was a state legislator,” Lt. Todd Hutchinson told the Orlando Sentinel.

Ironically, Representative Allen had sponsored a failed bill in the Florida statehouse earlier this year, the Lewdness and Indecent Exposure Bill, designed to increase the penalties for committing “unnatural and lascivious acts or exposure or exhibition of sexual organs committed within specified distance of certain locations.”

Since his election in 2000, he has been one of the most homophobic politicians in the Florida state senate.

He received the title of “Wicked Witch,” which is reserved for “The Worst of the Worst,” from Florida’s Rainbow Democratic Gay Lesbian organisation.

According to the biographical information provided on the Florida House of Representatives website, he is 48 and married with one child.

Mr Allen resigned from the troubled campaign of Senator McCain yesterday but said he would plead not guilty to the solicitation charge and has no plans to resign as a state representative.

Earlier this week two key strategists also left the campaign and the Senator, who was held by the VietCong as a prison of war for six years, has not been able to raise campaign funds to match his opponents.

He was a keynote speaker at the Conservative party conference in Bournemouth last year, and is seen as politically close to the ‘new’ conservatism espoused by David Cameron.