Billions of dollars have been embezzled from Russia's Sochi Winter Olympics funds, opposition members alleged on Thursday. 

Former Deputy Prime Minister Boris Nemtsov and Solidarity party member Leonid Martynyuk released a report Thursday which analyzed six months of Olympic spending data, claiming that the huge balloon in cost — from 2007's $12 billion estimate to the current $51 billion — is a result of "a monstrous scam."

The report estimated that between $25 billion and $30 billion was "stolen" via unfair bidding by government-favored companies, as well as secrecy in the spending of the funds allotted. 

"We account this irregularity for corruption, fraud, sloppiness and unprofessionalism," Nemtsov said at a press conference in Moscow.

At its current price tag, the Sochi Games are the most expensive Olympics in history, winter or summer. The London Olympics cost $14.3 billion by comparison. 

"It is obvious that Putin's friends are running the preparations for the Olympic Games," Nemtsov said, according to Radio Free Europe

"It is also obvious that one is reluctant to put his own friends behind bars. However, we cannot look at all this passively because the scale will only grow bigger. The embezzlement they are presiding over is not just some kind of children's game but a real threat to Russia's national security." 

The opposition leaders have called for an investigation by Russian prosecution, claiming that the stolen funds could have been used to build about 1,870 miles of high-speed roads or provide housing for 800,000 people in Russia, BBC News reported

However, some Olympics officials were not shocked by the allegations. 

"I don't recall an Olympics without corruption," Jean-Claude Killy, head of the International Olympic Committee's coordination commission for the Sochi games, said.

"It's not an excuse, obviously, and I'm very sorry about it, but there might be corruption in this country, there was corruption before. I hope we find ways around that," he added. 

Government officials have denied accusations of the widespread corruption in the funding and preparations for the games. 

The corruption accusations came the same day as the Sochi medal designs were released:

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