Ms Royal, 53, touched a raw nerve when she backed demands for Quebec’s “freedom”, and was rebuked by Stephen Harper, the Canadian Prime Minister.

The controversy comes with the left-wing favourite already on the defensive amid criticism of her campaign and speculation over difficulties in her relationship with her partner, François Hollande, the Socialist Party leader.

Although Ms Royal sought to backtrack yesterday, claiming her words on Quebec had been misinterpreted, the incident renewed turbulence in what had once seemed a smooth ride to the presidency.

After emerging from the relative obscurity of regional politics to become the darling of the French media, she now trails Nicolas Sarkozy, her centre-right rival, by four percentage points, according to the latest opinion polls.

Opponents have seized on her gaffes — praising China’s judicial system, contradicting international policy on Iran and failing to condemn Hezbollah, the extremist Lebanese militia group — to argue she is unfit for the presidency.

They say that the woman who presented herself as a breath of fresh air in a tired, male-dominated political world has been revealed as worryingly inexperienced.

“She is extremely lightweight on serious and sensitive subjects,’ Michèle Alliot-Marie, the Defence Minister, said. She is backing Mr Sarkozy.

Ms Royal faced further criticism for pledging legislation on domestic violence, apparently unaware that a similar law was already on the statute books. She has also been ridiculed for a linguistic faux pas on a recent visit to China, when she spoke of “bravitude” instead of “bravoure” (bravura).

The latest row followed a meeting in Paris with André Boisclair, the head of the proindependence Parti Québecois, on Monday. Interviewed by Canadian journalists, Ms Royal spoke of “common values, namely the freedom and sovereignty of Quebec”.

The outburst reawakened suspicions in English-speaking Canada that Paris is secretly pushing for the independence of francophone Quebec.

The response from Mr Harper was vicious. “Experience teaches that it is highly inappropriate for a foreign leader to interfere in the democratic affairs of another country,” he said.

Questioned on radio, Ms Royal insisted that she had never intended to call for the break-up of Canada. “It is not up to France to dictate to either the Quebeckers or Canadians what they must do,” she said.

Ms Royal also sought to counter speculation over her relationship with Mr Hollande, the father of her four children. “It is important that the rumours stop and that we are left alone,” she said.

The couple have been in the spotlight after disagreeing publicly over tax rises. Mr Hollande, who had wanted to run for the presidency himself before being swept aside by his partner, added to the feud when he was quoted in Le Monde as saying: “The thing about Ségolène’s charisma is that she hasn’t got any.” Asked why he had contradicted her line on tax policy, he replied:

“Line? What line?”

Ségolène says

As the Chinese say, one who has not come to the Great Wall is not brave. One who goes to the Great Wall conquers bravitude” (a distortion of the word ’bravoure’)

Thank you for being so frank. I agree with a lot of the things you have said, notably your analysis of the US” (in reply to a Hezbollah MP who had denounced “unlimited American insanity” and compared Israel to Nazi Germany)

Judicial co-operation is becoming stronger... Sometimes the justice is swifter than in France.” (on China’s legal system)

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