Barack Obama and Nicolas Sarkozy caught on microphone criticising the Israeli PM.

You'd think politicians would have learnt to check whether their microphones were switched off, by now -- but apparently not.

The latest to be caught out are Nicolas Sarkozy, and Barack Obama, who were caught criticising Binyamin Netanyahu in a private conversation at the G20 summit -- unaware that this private exchange was being broadcast to a small group of journalists.

The gaffe took place during a frank exchange where Obama took Sarkozy to task for not warning him that France would backing Palestine's request for membership of the UN cultural heritage agency, Unesco. Referring to the Israeli prime minister, Sarkozy told Obama: "I cannot stand him. He's a liar." The US President responded: "You're fed up with him? I have to deal with him every day."

Apparently, neither leader realised that microphones that had been attached for a press conference were still switched on. The comments initially went unreported, until French website Arrêt Sur Images reported it today. A Reuters journalist, also present, confirmed this account.