The leader of America’s powerful National Association of Evangelicals, a vocal supporter of George Bush and opponent of same-sex marriage, has resigned after being accused of paying for sex with a man.

The Rev Ted Haggard, a married father of five who is seen as one of the most influential conservative Christians in the nation, vigorously denied the allegations but said he could not "continue to minister under the cloud created by the accusations."

He also temporarily stepped aside from his position as head of the New Life Church in Colarado Springs – which has 14,000 members - while a church panel investigates the claims.

"I am voluntarily stepping aside from leadership so that the overseer process can be allowed to proceed with integrity. I hope to be able to discuss this matter in more detail at a later date", he said in a written statement.

Mr Haggard, who was appointed president of the 30 million-member association in March 2003, insisted the claims were untrue, saying: "I have never had a gay relationship with anybody, and I’m steady with my wife, I’m faithful to my wife."

The claims were made by Mike Jones, a male escort from Denver, who told the media that Mr Haggard had paid him to have sex every month for nearly three years. He claimed that the Reverend had snorted methamphetamine before their sexual encounters in order to heighten the experience, an allegation also denied by Mr Haggard.

Mr Jones said that he had voicemail messages from Mr Haggard as well as an envelope allegedly used to send him cash, which provided evidence of their secret trysts. "There’s some stuff on there (the voice mails) that’s pretty damning," he said.

The Associated Press reported that Ross Parsley, the acting senior pastor at the New Life Church, had told local station, KKTV-TV, that Mr Haggard had admitted that some of the accusations were true, but did not elaborate any further.

"I just know that there has been some admission of indiscretion, not admission to all of the material that has been discussed, but there is an admission of some guilt," Mr Parsley told the station.

The allegations come as voters in Colorado and seven other states prepared to consider bans on gay marriage in next week’s elections. Mr Haggard has publicly supported the measure, saying last year that he believed marriage was a union between a man and woman, rooted in centuries of tradition.

Mr Jones, 49, said that he had been prompted to make public his claims because of Mr Haggard’s stance on same-sex marriage.

He told local media: "It made me angry that here’s someone preaching about gay marriage and going behind the scenes having gay sex," he said.

"I just want people to step back and take a look and say, ’Look, we’re all sinners, we all have faults, but if two people want to get married, just let them, and let them have a happy life.’"

He claimed he had advertised himself as an escort on the Internet and that a man calling himself "Art" contacted him, whom Mr Jones recognised as Mr Haggard from television appearances.

Extracts from the alleged voicemails were broadcast last night by KUSA-TV, a Colorado TV station. "Hi Mike, this is Art," one call began, according to the station. "Hey, I was just calling to see if we could get any more. Either $100 or $200 supply."

The allegations could prove a setback for the US President as he strains to boost support for his party at next week’s elections.

Although the evangelical association is not as rigidly ideological and staunchly loyal towards the Republican Party as other evangelical groups, Mr Haggard has been a prominent supporter of Mr Bush. Last year, he featured in a list of Time magazine’s 25 most influential evangelical leaders, which noted his participation in conference calls with the White House.

Amidst the row, Jerry Falwell, a prominent conservative Christian and Republican Party stalwart, was quick to play down the organisation's role and Mr Haggard's standing among evangelicals.

"He doesn't really lead the (evangelical) movement. ... He is the president of an association that is very loosely knit and I've never been a member of it," Ms Falwell said in a CNN interview on Thursday.

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