"It is very disappointing because the mandate on which I am negotiating in the world trade talks... has been agreed by all the member states."
The British commissioner added: "I regret that Mr Sarkozy's intervention last night will make it harder for me."
Mr Sarkozy has accused Mr Mandelson and the head of the World Trade Organisation (WTO), Pascal Lamy, of preparing to sell out European farmers in the name of free trade in the so-called Doha Round of trade talks.
The talks, which began in 2001, have repeatedly stalled over the amount of state aid given to key industries in Western countries.
Mr Mandelson said food protectionism was "not going to feed the world's hungry", and that the talks were "too important" to be allowed to fail.
French deputy Jacques Myard, from the ruling UMP party, described Mr Mandelson's trade proposals as unacceptable.
France's EU presidency is off to a bumpy start
"We need to defend the [Common Agricultural Policy] in the interests of all Europeans," he told the BBC.
Speaking on French TV on Monday, Mr Sarkozy said Mr Mandelson and Mr Lamy "want to make us accept a deal under which Europe would commit to cutting farm output by 20% and reduce farm exports by 10%".
"That would be 100,000 jobs lost, I won't let it happen," he said.
A spokesman for Mr Mandelson said on Wednesday that the French president's figures were based on "a false assumption".
"The figures he is parading are not valid on the basis of current discussions in Geneva," Peter Power said.
The French presidency of the EU was already off to a bumpy start even before Mr Mandelson's rebuke.
On Tuesday, Mr Sarkozy criticised Polish President Lech Kaczynski when he said he would not ratify the EU reform treaty.
Mr Kaczynski said that to do so would be "pointless" after its rejection by the Irish.
The French have set out ambitious plans on immigration, the environment and defence for their presidency.
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