The report, culling information from government budgets and data from companies involved in construction for the Games, is the latest to pour scorn on a project on which president Vladimir Putin has staked his personal and political prestige.
Mr Navalny, who led protests against Mr Putin in Moscow two years ago, said the information challenged the president’s figure for spending on the Sochi Games, which open in the Black Sea resort on 7 February.
“Russia’s overall expenses have already reached $50 billion (£30bn), which makes the Russian Olympics five times more expensive than the Vancouver [Winter] Olympics [in 2010,” the report said. “Officials and businessmen also took part in the Games and turned them into a source of income.”
The report said Mr Putin had helped enrich friends by awarding them contracts to build large-scale Olympic venues at a cost several times above those of similar venues elsewhere.
Mr Putin has dismissed claims of corruption and challenged those who made allegations to back up their claims.
In an interview earlier this month, he said: “We don’t see any large-scale instances of corruption during our preparations … in Sochi. If anyone has any information about corruption in Sochi, please hand it over, we will be glad and grateful.”
The president’s figure for total spending on the Games has diverged from those provided in other estimates, including one of $50bn from another Russian opposition figure, who accused contractors of stealing half the money allocated for the Winter Olympics.
Earlier this month, Mr Putin said Russia had spent only about $6.5bn on preparations for the Games, in sharp contrast with an estimate from deputy prime minister Dmitry Kozak, who last year said Russia would spend some $50bn.
Mr Navalny’s report said more than $12bn in state funds had been divided between two companies, Olimpstroy and state monopoly Russian Railroads, to build venues and roads. It said $8.7bn had been spent to build a railway and motorway nearly 50km long that leads to the Rosa Khutor ski resort, the venue of the Olympic mountain sports.
Part of that, Mr Navalny said, went to friends of the president.
His report, which won little attention in Russia’s tightly controlled media, also contradicted government statements that private companies’ money had made up for more than half of the investment in Sochi. It said private companies had put less than 4 per cent of the cost.
“In their statements, officials referred to investments of Gazprom, Sberbank, Russian Railways and other government-affiliated entities as private investments,” the report said, adding that under international accounting standards, such investments would be considered state money.
Subcontractors say that corruption has been endemic in the lead up to the Sochi Games.
Former deputy premier Boris Nemtsov released a report last year comparing Sochi’s Olympic infrastructure costs with those of similar venues outside of Russia and claiming that half the budget allocated for construction in the Russian resort had been stolen.
• For more on the report, go to http://sochi.fbk.info/en/award/