The Russian media have claimed that the singer has selected the Konstantinovsky Palace just outside Russia's former capital for the ceremony.
Sir Elton announced recently that he planned to formalise his relationship with Mr Furnish, a film-maker, on 21 December, the same day as legislation allowing same-sex civil partnerships comes into force.
The couple were said to be "scrabbling around" for a suitable venue but have so far not disclosed a location. Russian media insist it is St Petersburg.
The claim, which has not been confirmed by the singer or the palace, appears to be based on the fact that Sir Elton was in St Petersburg with Mr Furnish last month for a charity event. It was then, it is claimed, that the couple made the "wedding" plans.
True or not, the reports have caused a lively scandal fuelled bycondemnation from nationalist Vladimir Zhirinovsky's party.
Nikolai Kuryanovich, an MP for the Liberal Democratic Party of Russia and Mr Zhirinovsky's right-hand man, has filed a complaint to the Russian Minister of Culture and to the administration of President Vladimir Putin demanding the ceremony not be allowed to take place.
The MP asked the government to intervene to prevent the "defilement" of an important historical monument, calling the purported wedding plan "unacceptable" and "twisted". "The marriage of homosexuals is the end of the British court [society]," he said on the party's official website. "First Prince Harry was forced to drop his trousers by a black sergeant before becoming an officer and now they have allowed same-sex marriages." Sir Elton's purported plans were "godless", he added.
The Konstantinovsky Palace is listed as one of Mr Putin's official residences and has had £161m lavished on it in recent years. Though private functions there are forbidden, there is an hotel complex within its grounds which is where Russian media claim the wedding will take place. Arguing that he was protecting the "morals" of the Russian people, Mr Kuryanovich advised Sir Elton to get married in "dying" western Europe. He urged Russia not to follow in Britain's "sad" footsteps when it came to the issue of homosexual relationships. Unnamed Russian MPs were said to agree and to have said that it would be "a disgrace for Russia" if the wedding was allowed to take place. Though Mr Zhirinovsky's party is not in power, its pronouncements are widely reported and seen as a barometer of popular opinion. Earlier this year Mr Kuryanovich tabled legislation forbidding Russian women to marry foreign men on the grounds that the Russian gene pool was being dangerously diluted.
Same-sex marriage is not legal in Russia, but there is no law banning it. In February the country's Supreme Court rejected a plea by a gay politician and his journalist partner seeking amendments to the family code to allow same-sex marriages. In the Soviet era, homosexuality was illegal but it was decriminalised in 1993. Acceptance of same-sex relationships is in its infancy.
Sir Elton and Mr Furnish have applauded the Government for bringing forward such legislation. Mr Furnish told the gay lifestyle magazine Attitude: "From a social standpoint, I think it's hugely significant.It is a major change. I applaud Britain for embracing the diversity of our society."Reuse content