In media interviews Princess Helene of Yugoslavia, estranged wife of Thierry Gaubert, also linked him with Nicolas Bazire, the best man at Sarkozy's wedding, and Ziad Takieddine, the alleged middleman in an arms deal with Pakistan.
All three men have been charged by police investigating alleged kickbacks on the arms deal and illegal funding of former prime minister Edouard Balladur's failed 1995 presidential campaign.
Sarkozy was the campaign's spokesman at the time of the alleged payments, as well as budget minister, but insists he had nothing to do with funding.
"I confirm what I said about my husband's trips, especially abroad," the princess told Europe 1 radio, saying he used to go from Paris to Geneva and back via London.
"There was money, but I don't know where it came from," she said. "There was my husband and Mr Takieddine."
In a separate interview with the daily Le Monde, Princess Helene, 45, said her husband "went to Switzerland about once every two months".
"He went systematically via London, telling me he wanted to avoid customs checks on the French-Swiss border," she added.
"He told me one day that he was going to fetch cash from Switzerland to give it to Nicolas Bazire."
Bazire, 54, the manager of Balladur's presidential campaign and now a director of luxury goods giant LVMH, and Gaubert, 60, an advisor to Sarkozy when he was budget minister, were charged this week with misuse of public funds.
Takieddine was charged last week with fraud over arms contracts with Pakistan and Saudi Arabia in which he was allegedly the middleman.
Sarkozy allies have denounced what they claim is a plot against the French president expected to seek re-election next April. Opinion polls show he is likely to lose to the victor of the ongoing Socialist primary.
Sarkozy's Elysee palace office said Thursday that the president had had no role in financing Balladur's campaign.
However his signature as budget minister at the time does reportedly appear on documents setting up a front company to handle commissions on a submarine deal.
Questions over the arms contract erupted when investigators began probing whether a 2002 bomb attack in Karachi that killed 11 French engineers working on the project was a revenge attack for promised bribes not paid.
Balladur's presidential bid was defeated by Jacques Chirac, who on coming to office, cancelled payments to middlemen on the contract, allegedly angering Pakistani intelligence officers who stood to profit from the deal.
Henri Guaino, Sarkozy's special advisor, meanwhile, said on Saturday the president was "in no way involved" in the financial aspects of the Karachi affair, adding that Bazire had never been one of Sarkozy's "close advisors".
"Mr Bazire was cabinet chief of the prime minister and Balladur's campaign chief," Guaino told French television.
"He is a friend of the president, but he is not his close advisor and has never been."
"And Mr Gaubert has not been an aide to the president for more than 15 years," he added.