New York ? The federal probe into Eliot Spitzer’s alleged use of high-priced prostitutes took on a partisan tinge Sunday with news that a Republican political operative provided the FBI with salacious details of the former governor’s trysts four months before he resigned.

In a Nov. 19 letter, an attorney for Roger Stone, once a consultant to Republican State Senate Majority Leader Joseph Bruno, said Spitzer had spent “tens of thousands” of dollars on prostitutes.

“It is also my client’s understanding … that Governor Spitzer did not remove his mid-calf length black socks during the sex act,” wrote attorney Paul Rolf Jensen of Costa Mesa, Calif., to special agents in the FBI’s New York field office. “Perhaps you can use this detail to corroborate Mr. Stone’s information.”

It remained unclear whether Stone’s tip played a role in the probe of Spitzer and the Emperors Club VIP prostitution ring broken up March 7.

However, a source familiar with the Spitzer probe said Sunday that it began well before the letter was sent. Sources have described the investigation as beginning in October with tips from banks that noticed unusual wire transfers between Spitzer’s account and shell companies set up by the prostitution ring. Spitzer resigned March 13.

Stone is a longtime GOP operative who began his career working for Richard Nixon. In 1996, he resigned from Republican Bob Dole’s presidential campaign when an ad seeking a sexual threesome with him and his wife was discovered in a Washington swingers magazine.