French law bans candidates from receiving cash payments above 6,300 pounds, but local news website Mediapart claims that the massive donation was laundered through bank accounts in Panama and Switzerland, the 'Daily Mail' reported.
A document made public in Paris is said to show that the French leader and the former Libyan dictator made an illegal financial deal that propelled Sarkozy to power in 2007.
Written in Arabic and signed by Mussa Kussa, Gaddafi's former intelligence chief, in 2006, it refers to an "agreement in principle to support the campaign for the candidate for the presidential elections, Nicolas Sarkozy, for a sum equivalent to Euros 50 million", the report said.
A governmental briefing note among papers available to 'Mediapart' points to numerous visits to Libya by Sarkozy and his colleagues which were aimed at securing funding.
One, said to have taken place on October 6, 2005, led to "campaign finance to NS" being "all paid" -- assumed to be a reference to Sarkozy who was at the time an ambitious interior minister raising money for his presidential election campaign.
Mediapart claims that the 50 million pounds referred to in the note was laundered through accounts including a Swiss one opened in the name of the sister of Jean-Francois Cope, the leader of Sarkozy's ruling UMP party, and the President's right-hand man, the British newspaper said.
The money was then allegedly distributed through an arms dealer called Ziad Takieddine, who was acting as a middle man between Arab despots and French politicians, the report said.
But, President Sarkozy's campaign spokesperson Nathalie Kosciusko-Morizet has dismissed the report as "ridiculous" and a "clumsy diversion" orchestrated by supporters of socialist opponent Francois Hollande.