Hours before he took over the presidency of the European Council, Sarkozy launched a fresh attack on Mandelson's position in WTO negotiations. Monday night, he told French television: “[WTO director general] M. Lamy and M. Mandelson would like us to accept an agreement under which Europe would undertake to cut its agricultural production by 20% and its agricultural exports by 10%. This is 100,000 job cuts and I will not let it happen.”

Sarkozy's arguments are reminiscent of those of the IFA, which claimed that dozens of thousands of jobs would disappear in Ireland alone if the proposed tariff cuts supported by Mandelson in WTO negotiations are implemented.

An EU Commission spokesman rejected Sarkozy's figures, arguing that the current proposals would lead to a 1.1% drop in EU agriculture production and a 2.5% fall in employment in the farming sector by 2014.

The commissioner for trade was nowhere to be seen at the official ceremonies marking the opening of the French presidency in Paris on Tuesday. When Sarkozy and his government greeted European Parliament president Hans-Gert Pöttering, the EU's foreign policy chief Javier Solana and commissioners under the Arc de Triomphe, Mandelson was the only one missing. A busy schedule also allowed him to bypass the official dinner in honour of the Commission at Sarkozy's Elysée palace that evening.

While he did travel to Paris on Tuesday, Mandelson's brief comments to journalists there amounted to a sharp rebuttal of the French president's criticism. “It poses a great problem because as the negotiator of the EU, I need the unity of the member states behind me,” Mandelson said. He later told the BBC: “I am being undermined and Europe's negotiating position in the world trade talks is being weakened. And I regret that.”

Mandelson insisted that he had not exceeded his mandate in world trade negotiations. Under EU rules, the commissioner for trade represents all member states in WTO talks, but each of them can still veto an agreement he enters into if they consider that he has gone beyond his remit.

Sarkozy's comments came on the day France's leading farmers' union FNSEA, together with the union of young farmers and the federation of French co-ops, wrote him a letter calling for inflexibility on WTO negotiations. “For a long time, there has been the temptation to seal an agreement that would sell off agricultural trade and threaten our food sovereignty in exchange for an uncertain liberalisation of goods and services”, they wrote. The letter added: “We rely on you to stop and refuse a bad agreement in the WTO and to give a new impetus for balanced world trade.” The French president could not have stuck any closer to the farmers' position.

The latest row between Sarkozy and Mandelson happened days after WTO director general Pascal Lamy called a last-chance ministerial meeting to conclude the Doha round of world trade negotiations in Geneva from July 21st. The conference is expected to start with bilateral and group talks between representatives of WTO member states and to end with a formal meeting of the Trade Negotiations Committee to endorse a formal deal including an amended agricultural text.

Last Friday, Lamy said: “I know that this is not without its risks, and my sense today is that the chances of getting there are today over 50%.” He added that unless an agreement is sealed in July, it is likely to be delayed until next year – i.e. after the US election in November.

By chasing the issue publicly as negotiators are discreetly scrambling to find an agreement this month, Sarkozy could sink the current talks and postpone the prospect of a deal indefinitely. “Until last August, the world underwent six years of strong growth, between 3 and 5%, without an agreement”, he said. “Don't come and tell me that growth is conditional upon an agreement.”