Prominent opposition activists in Russia have denounced next year's Winter Olympics as a monstrous scam, saying that half the $US50 billion spent on them has been stolen.
The report by Boris Nemtsov and Leonid Martynyuk says nepotism, censorship and the absence of fair competition has contributed to making the games the most expensive in history.
They say that the final cost of staging the event will be more than four times higher than the original price tag of $12 billion announced by President Vladimir Putin.
The Black Sea resort of Sochi won the right in 2007 to hold next year's Games, and preparations for the event began soon after, the BBC reports.
The activists' investigation alleges that many of the most lucrative projects were not put out to tender and have enriched only the oligarchs and Mr Putin's cronies.
A Russian official has dismissed the claims.
International Olympic Committee (IOC) spokesman Mark Adams said it appeared Russia was taking any corruption claims related to the Olympics seriously.
Mr Nemtsov, a former deputy prime minister, and Mr Martynyuk, a member of the Solidarity movement, released their report on Thursday after analysing Olympic-related data for six months.
The authors say they reached their conclusions by looking at the gap between the original estimate and the final cost and also comparing it with cost overruns at previous Olympics.