The US National Security Agency (NSA) spied on French presidents Jacques Chirac, Nicolas Sarkozy and Francois Hollande in 2006-12, WikiLeaks says.
In a press release WikiLeaks announced that is has began publishing what it calls 'Espionnage Élysée', a collection of top secret intelligence reports and technical documents from the NSA.
WikiLeaks spokesman Kristinn Hrafnsson said he was confident the documents were authentic, noting that WikiLeaks' previous mass disclosures have proven to be accurate.
"While the German disclosures focused on the isolated fact that senior officials were targeted by US intelligence, WikiLeaks' publication today provides much greater insight into US spying on its allies, including the actual content of intelligence products deriving from the intercepts, showing how the US spies on the phone calls of French leaders and ministers for political, economic and diplomatic intelligence," WikiLeaks said.
In the wake of the allegations current president Francois Hollande called an emergency national defence council meeting.
The meeting will be held at 9am on Wednesday " to evaluate the nature of the information published by the press on Tuesday evening and to draw useful conclusions."
The most recent document from May 22, 2012, days before Francois Hollande took office.
It reveals that the French leader "approved holding secret meetings in Paris to discuss the eurozone crisis, particularly the consequences of a Greek exit from the eurozone".
WikiLeaks founder Julian Assange said: "The French people have a right to know that their elected government is subject to hostile surveillance from a supposed ally.
"We are proud of our work with leading French publishers Liberation and Mediapart to bring this story to light. French readers can expect more timely and important revelations in the near future."
US State Department Spokesman John Kirby said: "We do not comment on the veracity or content of leaked documents." France has made no comment.