French president Nicolas Sarkozy and German chancellor Angel Merkel before the G20 talks. Photograph: Eric Feferberg/AFP/Getty Images

Nicolas Sarkozy has never been one to endear himself to his fellow heads of state. He has irritated with his boastfulness, exhausted with his hyperactivity and offended with his tendency to launch televised policy decimations and send text messages during meetings.

But, impressive though his track record is, he may now have outdone even himself. In the space of just one lunchtime, the French president has managed to belittle Barack Obama, patronise Angela Merkel and insult José Luis Zapatero by questioning his intellectual firepower.

According to those present at the lunch, an intra-parliamentary group of 24 politicians working on the global financial crisis, the host's unusual political candour began with the US president, whose star status and media adulation he is understood to envy.

"He said that Obama had a subtle intelligence but that he was recently elected and had never run a state or an authority before," Jean-Pierre Brard, a Communist MP, told the Guardian. Another guest quoted Sarkozy in the Libération newspaper as saying: "There are numerous things on which he [Obama] hasn't got a position and ... he is not always up to scratch with decisions and efficiency."

Enjoying his chance to cast himself as the hero of the global fight against the downturn, Sarkozy ploughed on with some barbed comments about Merkel's leadership during the crisis.

"Once she realised the state of her banks and her car industry, she had no choice but to come round to my position," he said.

The remarks are unlikely to win him any popularity points with the German chancellor who, despite her display of unity with Sarkozy in London last month, is known to find the hyperactive, over familiar president highly irritating.

In a meal peppered with ill-advised humour, it was not until dessert, however, that Sarkozy delivered his punchline. Discussing a recent policy move by the Spanish government which had taken France, according to Sarkozy, as its "example", one Socialist MP piped up and said there were "a lot of things to be said about Zapatero".

Responding swiftly, Sarkozy said: "Perhaps he's not very intelligent." The remark - emphatically denied by the Elysée but confirmed by sources present at the lunch, held on Tuesday - was greeted with an icy silence yesterday in Madrid, where the president is due on an official visit later this month.

But the Spanish media reacted with incredulity and headline writers were straining to come up with different words for "stupid". MPs who had attended the lunch were deluged with phone calls from journalists determined to find out the truth.

The president rounded off his explosive déjeuner by taking a swipe at an historic enemy from the French left, the former prime minister Lional Jospin, saying: "But I know people who were very clever and who did not make the second round of the presidential election."

The most important thing in democratic politics, Sarkozy is said to have declared, is to be savvy enough to cling on to power. Praising his Italian counterpart - no stranger to the occasional gaffe himself - Sarkozy reportedly said: "The important thing in democracy is to be re-elected. Look at [Silvio] Berlusconi. He has been re-elected three times."

One MP told the Guardian Sarkozy was also keen to praise Gordon Brown and Tony Blair's three election victories.

Less fortunate was José Manuel Barroso, the president of the European Commission, whom Sarkozy dismissed as having been "totally absent from the G20".

"Nul n'est prophète en son pays" est complêtement dépassé dans Sarkoland.