French president Nicolas Sarkozy last night called for a new fairer world order and attacked the soaring cost of oil.

In a speech in the City of London at the end of his two-day state visit to Britain, he said he was "deeply concerned" with what was going on with commodities, particularly oil.

"I'm worried to know that when I was minister of finance, a barrel of Brent was $42, right now it stands at $100, give or take a few dollars," he said. "And yet it costs the same amount to extract that same barrel of Brent."

The president said one could not talk about a stable world when some countries did not have electricity several hours a day, while others did not know what to do with earnings they got from commodities. "I wanted to say to the British government, we mustn't defend the established order, we've got to defend a fair world order."

Mr Sarkozy said that, while he championed freedom and competition, there was a need for rules and regulations, and France would be imposing tough rules on companies in terms of carbon emissions. "We have to safeguard the future of our planet and our children," he said.

Mr Sarkozy abandoned his planned speech for his address at the banquet in honour of himself and his wife, Carla, at London's Guildhall. He also paid tribute to the British economy's recovery from near-collapse in the 1970s and said the French must learn from the British people's "intelligent approach to work".

Earlier, the Prime Minister and the president pledged to "strengthen and deepen" relations between the two countries across a range of issues from climate change to Afghanistan. At a press conference held at Arsenal's Emirates Stadium in north London, Mr Brown described as "historic" the state visit by the French president. For his part, Mr Sarkozy, who, in an address to both Houses of Parliament on Wednesday lavished praise on Britain, said he was looking forward to a lasting improvement in relations between London and Paris.

"It is not simply a matter of a one-night stand. I believe that we can go in to next-day breakfast as well," he said.

He added that he had been "deeply moved" by the positive coverage his wife, Carla, had received in the British press over the past two days.

Mr Brown said he believed the state visit signified "a new stage in the dynamic relationship between Britain and France." He said they had agreed to co-operate on a range of issues from reform of international financial regulations and institutions to voting together on changes to international bodies such as the UN Security Council.

The Prime Minister welcomed Mr Sarkozy's promise to send more troops to Afghanistan while stressing the need for "greater burden sharing" by other Nato members when they meet next month in Bucharest.

Mr Brown also said they had agreed a common approach to the problems in Burma and Darfur and that they both urged "restraint and dialogue" in resolving the crisis in Tibet.

While Mr Brown emphasised that British athletes would attend the Beijing Olympics this year, Mr Sarkozy warned he will be "sounding out" EU member states over a possible boycott - the one discordant note during the visit in which the two leaders claimed the old "entente cordiale" between the two nations had been superseded by a new, warmer "entente amicale."

The president and his wife arrived 45 minutes later than expected at the Guildhall. The First Lady wore a floor-length, wine-coloured gown with a wrap for her bare shoulders.

The menu comprised of honey-roasted quail, timbale of scallop and sea trout, tournedos of British beef, followed by a trio of British classics - marmalade creme brulee, poor Knights of Windsor and treacle tart.