We will win, Mr Obama. You and me, together.

Nicolas Sarkozy has been accused of using a video conference with Barack Obama to boost his election campaign. In an unprecedented move in French diplomacy, newscasts on several TV channels showed the first few minutes of a video link-up between the French president and his Washington counterpart.

Days before the 22 April first-round vote in the French presidential election, the rare glimpse of banter between world leaders shows Obama saying of the campaign, "It must be a busy time." He adds: "I admire the tough battle you are waging." Sarkozy replies, grinning and with arms folded: "We will win, Mr Obama. You and me, together." The cameras leave before the presidents talk about Syria, Iran and oil.

The Socialist party accused Sarkozy of breaking diplomatic protocol and embarrassing France on the world scene in order to boost his struggling campaign for re-election, saying the images "weakened France's credibility in Washington and across the world".

The SNJ-CGT journalists' union at the state broadcaster France Televisions condemned what it deemed "a grotesque communications operation" by Sarkozy, calling it a "surrealist sequence" of electoral media strategy.

French media questioned whether the White House knew the footage would be made public or whether Obama was set up. But Washington told Le Monde it had indeed been aware that cameras were authorised to film the first few minutes of the video conference.

Angelique Chrisafis in Paris

guardian.co.uk, Sunday 15 April 2012 11.50 BST