A political rival has admitted that he tipped off the FBI about the former New York Governor’s use of prostitutes, effectively ending Elliot Spitzer’s career in public office to score a victory in a bitter feud.

Roger Stone, a controversial Republican operative, alerted authorities four months before the Democratic governor was forced to step down in a sex scandal. Mr Stone told the FBI, through a letter from his lawyer, that Mr Spitzer “used the services of high-priced call girls” while in Florida.

“The governor has paid literally tens of thousands of dollars for these services. It is Mr Stone’s understanding that the governor paid not with credit cards or cash but through some pre-arranged transfer,” the letter said.

“It is also my client’s understanding from the same source that Gov Spitzer did not remove his mid-calf-length black socks during the sex act. Perhaps you can use this detail to corroborate Mr Stone’s information.”

The letter, dated November 19, was released after intense speculation about Mr Stone’s possible role in Mr Spitzer’s downfall this month after he was exposed as “Client 9” of an international prostitution ring that charged up to $5,500 (£2,800) an hour.

The FBI refused to comment on what part the letter played in its investigation. Court papers say that the investigation into the Emperors Club VIP prostitution ring began “in or about October 2007”, suggesting that FBI agents were already on Mr Spitzer’s trail. Previous reports said that the investigation was triggered by suspicious money transfers from Mr Spitzer’s accounts.

Mr Stone, who spends part of the year in Miami Beach, is a selfconfessed practitioner of political “black arts” who once worked during the Watergate era for President Nixon, planting a mole in the campaign of a Democratic presidential rival.

His career as a political consultant almost came to an end in 1996 when he was forced to quit Bob Dole’s “family values” presidential campaign after provocative photographs of him and his wife, Nydia, a former model, appeared in swinger magazines.

He helped to orchestrate the so-called Brooks Brothers riot in Miami, when angry Republicans in pinstriped suits shut down the 2000 presidential election recount in Dade County, Florida. Though a Republican, he also gave advice to the Rev Al Sharpton, the black civil rights leader, in his 2004 presidential campaign.

Mr Stone held a $20,000-a-month post last year as a political consultant to Joseph Bruno, the state senate majority leader and Mr Spitzer’s main rival in the New York legislature. He was forced to resign in August after he allegedly left an abusive telephone message for Mr Spitzer’s father.

Mr Stone accused Bernard Spitzer, a multimillionaire property developer, of secretly financing his son’s political campaigns. Private investigators traced the call to Mr Stone’s flat on Central Park South, in a smart area of New York.

A voice that appeared to be Mr Stone’s said: “This is a message for Bernard Spitzer. You will be subpoenaed to testify before the Senate committee on investigations on your shady campaign loans. You will be compelled by the Senate Sergeant at Arms.

“If you resist this subpoena, you will be arrested and brought to Albany — and there’s not a goddamn thing your phoney, psycho, piece of s*** son can do about it.

“Bernie, your phoney loans are about to catch up with you. You will be forced to tell the truth. The fact that your son is a pathological liar will be known to all.”

Mr Stone, a partner in a Fort Lauderdale public relations company, instructed his lawyer to expose the New York governor’s use of prostitutes after the FBI asked to talk to him about an unspecified matter.

He told the Miami Herald that he learnt about the governor’s behaviour from a high-end call girl at an adults-only club called Miami Velvet who confided in him that she was disappointed to have missed a chance to entertain Mr Spitzer.

Instead, her friend met Mr Spitzer and noted that he kept his socks on, Mr Stone said.

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