In an interview with the Mediapart investigative news site, Franco-Lebanese businessman Ziad Takieddine said he had made three trips from Tripoli to Paris in late 2006 and early 2007 with cash for Sarkozy's campaign.
Each time he carried a suitcase containing between 1.5 and 2.0 million euros in 200-euro and 500-euro notes, Takieddine told the site in a video interview, saying he was given the money by Kadhafi's military intelligence chief Abdallah Senussi.
Sarkozy, who is bidding to recapture the presidency in next year's election, has for years been dogged by allegations that he accepted millions from Kadhafi during his successful 2007 run for the top office.
During questioning in a separate case, Takieddine accused Sarkozy of having been in Kadhafi's pocket in 2006-07 but he had never previously claimed to be the bagman.
The allegations against Sarkozy first emerged in March 2011, when the French leader was campaigning for the NATO-led military intervention that helped overthrow Kadhafi.
"Sarkozy must first give back the money he took from Libya to finance his electoral campaign," Kadhafi's son Seif al-Islam, who is now in jail in Libya, demanded.
A year later, as Sarkozy was campaigning for a second term, Mediapart published a document signed by former Libyan intelligence boss Musa Kusa referring to an agreement for 50 million euros ($54 million at current rates) in backing from Tripoli.
Sarkozy, who lost his 2012 re-election bid, vigorously denied the allegations, claiming the document was a fake.
Takieddine's video testimony comes five days before Sarkozy goes up against former prime minister Alain Juppe and other rivals in a primary to choose the candidate of the French right in next year's presidential vote.
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The first round of the two-stage primary takes place on Sunday.
Takieddine said he delivered the cash directly to the interior ministry, which Sarkozy headed at the time.
He said he was received on the first two occasions by Claude Gueant, Sarkozy's then cabinet chief whom he later made his interior minister.
The businessman, who said he wanted to tell all about "the mafia state in which we are living", said he set down the cases in Gueant's office but did not discuss the contents with him.
On the third occasion, he was received by Sarkozy himself in an apartment on the first floor of the ministry, he claimed.
After setting down the case, he said Sarkozy spoke to him briefly about a group of Bulgarian health workers imprisoned in Libya whose liberation Sarkozy negotiated later that year.
But he studiously avoided the topic of the briefcase.
In 2012, Senussi, who is also imprisoned in Libya, told investigators he "personally supervised" the handover of 5.0 million euros towards Sarkozy's campaign.
But despite several other such former high-ranking members of Kadhafi's regime making similar claims, French investigators have yet to find any evidence of illegal campaign funding, according to AFP's sources.
Sarkozy has brushed off the allegations as the claims of vindictive Libyan regime members, furious with him for leading the intervention that ended Kadhafi's 41-year rule.
The 61-year-old right-winger, who is trailing presidential frontrunner Juppe in opinion polls, is embroiled in several scandals.
He has been charged with influence peddling in a separate affair and with illegal financing of his 2012 campaign. Sarkozy has accused the judiciary of trying to stymie his comeback ambitions.