Is she Jackie Kennedy or Marie Antoinette? The question about Cécilia Sarkozy, the unpredictable French first lady, gathered steam yesterday after she stood up George and Laura Bush, embarrassing her husband and drawing criticism at home.

Few in France believed the official excuse for Mrs Sarkozy's decision at an hour's notice to miss a Saturday barbecue with the US presidential family at Kennebunkport, Maine. An apologetic Mr Sarkozy turned up an hour late from the couple's New Hampshire retreat, explaining that his wife had been hit by a severe throat infection.

Yet on Sunday, Mrs Sarkozy, 49, was seen strolling in shorts with friends around the town of Wolfesboro. Commentators talked of a diplomatic incident.

"Cécilia Sarkozy had a lightning infection," Le Figaro, the most pro-Sarkozy newspaper, noted drily. "The day before she was in good form, and the day after she was cured."

Both Libération and Le Monde said that her conduct had put a damper an otherwise successful US-French bonding session.

Agence France-Presse, the national news agency, said that Mrs Sarkozy had "sharpened her image of a first lady who is secret, unpredictable, even disconcerting - the opposite of her predecessors at the Elysee Palace."

The missed lunch fitted a pattern that has become known as "the Cécilia problem" or "le mystère Cécilia". This arises from the contrast between Mrs Sarkozy's apparent desire to enjoy her Elysée Palace role while also appearing to disdain it. "What does the president's wife want?" asked Le Telegramme newspaper. "Does she want to live her life without constraints? In that case why accept invitations such as the one from Laura Bush?"

The tall and stylish former Cécilia Ciganer, a university drop-out and onetime model, was absent from view for much of her husband's campaign and even failed to vote for him. They had suffered marital trouble and she had recently said that the idea of being first lady "bores me stiff".

Yet Mrs Sarkozy, who rarely smiles and never speaks in public, blossomed after his election as an ultimate première dame. Her hyperactive husband, who makes frequent public declarations of his love, joined the media in calling his wife a new Mrs JFK.

At a G8 summit in Germany in June, however, the Prada-wearing Mrs Sarkozy caused an incident by cutting short her attendance with Mrs Bush and other leaders' spouses. Her ratings soared in late July when Mr Sarkozy sent her to Libya on a successful mission to accompany home Bulgarian nurses who were released after eight years imprisonment.

Mrs Sarkozy's unconventional behaviour has stirred fascination and, increasingly, disapproval, with comparisons to Queen Marie-Antoinette, consort to Louis XVI, who died on the guillotine. "We are deep in the Marie-Antoinette syndrome," said Nicolas Domenach, deputy editor of Marianne magazine and a biographer of Mr Sarkozy. "In France we all desire a queen at the same time as we want to settle accounts with the monarchy." Such comparisons are coming from the left because of the Sarkozy couple's fondness for opulence and their circle of rich friends.

The image of the Queen who played in her little mansion at Versailles while France neared revolution was invoked by Mathilde Agostinelli, Mrs Sarkozy's closest friend and media director for Prada in France. Mrs Sarkozy's weekends at the president's Mediterranean retreat "makes me think of a modern Marie-Antoinette, happy in her Petit Trianon," Ms Agostinelli told le Nouvel Observateur magazine.

Mr Sarkozy's emotional dependence on his turbulent wife is the talk of Paris. The action-man president makes no secret of his need for her approval. Late on the night of his election, when she finally turned up to celebrate, he danced the sirtaki before her (and photographers) in an an attempt to cheer her up. At his first Bastille Day garden party, Mr Sarkozy, in euphoric mood, confided to reporters: "Basically, Cécilia is my only worry."

The president, who went to extraordinary lengths to win back his wife when she deserted him for an events organiser in 2005, has said that pair will decide on the nature of her official role next month.

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