Top French intelligence officials Bernard Barbier and Patrick Pailloux travelled to Washington to demand an explanation for for an attempt to compromise the Elysée presidential palace's communications system, according to a briefing note prepared in April and published by Le Monde.
At the time outgoing president Nicolas Sarkozy's teams were still working at the Elysée as he fought an unsuccessful battle to remain in power.
The Americans, who were so anxious not to upset the French that the note spelt out how to pronounce their names, denied being behind the hacking and said that most of their closest allies - Australia, Britain, Canada and New Zealand - also denied involvement.
But the branch of the NSA which handles cyberattacks, Tailored Access Operations (TAO) refused to vouch for Israel.
"TAO intentionally did not ask either Mossad or [Israel's cyberintelligence unit] ISNU whether they were involved as France is not an approved target for joint discussions," the note said - a statement that the Le Monde article, coauthored by former Guardian journalist Glenn Greenwald, interprets as a hint that the Israelis were responsible.
The attacks have been previously reported by French media, who said they were an attempt to insert monitoring devices into the system, but it is unclear whether the presidential networks were compromised for any time.
Both US and French intelligence work closely with Mossad but not without a certain amount of mistrust.
A 2008 NSA note leaked by the Guardian judged the Israelis "excellent partners in terms of sharing information " but added that Mossad is "the third most aggressive intelligence service in the world against the United States".
France is also reported to have protested about Mossad's use of its soil to plan operations such as 2010 assassination in Dubai of Mahmoud Al-Mabhouh of the Palestinian movement Hamas.
"Israel is a country which is a friend, ally and partner of France and does not carry out any hostile activity which could pose a threat to its security," the office of Israeli Prime Minister Benjamin Netanyahu told Le Monde.