It would effectively end any ambitions Mr Sarkozy has of seeking re-election due to a "conflict of interest" between business and politics.
Mr Sarkozy has often said he hoped to make money after leaving politics.
Mediapart said the former leader's plan to launch a private equity fund in London is currently in the "exploratory" stage and that no company has yet been officially created.
Sources close to Mr Sarkozy dismissed the alleged plan as an "intellectual construction", with one telling The Daily Telegraph the former leader "does not confirm anything in the article".
However, the website cited "very precise financial and industry sources" as saying plans are definitely afoot.
It said Mr Sarkozy's efforts to set up the fund cropped up in computer files seized last summer at his offices and Paris home.
These were obtained during raids by judges investigating allegations that l'Oreal heiress Liliane Bettencourt illegally funded Mr Sarkozy's 2007 presidential campaign.
With the help of Alain Minc, a businessman and confidant, Mr Sarkozy has since October been seeking to recruit investors during a string of conferences, the first two for Brazilian group PTB Pactual, which has a large private equity arm.
In one of his trips, he reportedly approached Temasek, a Singapore sovereign fund, proposing it invest a 200 million-euro stake in the fund, but the fund declined to take part, Mediapart said.
Yesterday, Mr Minc denied playing any role in creating such a fund.
"It is absurd to think he would move to London and stop paying taxes in France." "Nicolas Sarkozy doesn't need me to meet the world's biggest funds," he told Le Figaro. "He has a thousand contacts and hasn't made up his mind about what he wants to do."
Laurent Mauduit the Mediapart journalist who wrote the article, said: "I note Minc denies things I never wrote." "I never said he would physically move to London but planned to set up his company there," he told The Daily Telegraph.
Last June, David Cameron who backed Mr Sarkozy in his failed re-election bid infuriated Socialist president Francois Hollande by promising to "roll out the red carpet" to French businesses wishing to move to Britain.
One French minister said he must have been "drunk" at the time.