Six French aid workers found guilty of attempting to abduct 103 children in Chad were jailed on their return to France last night. Their repatriation followed a high-level agreement between France and its former colony.

The members of Zoe’s Ark, a children’s charity in France, were given eight years’ hard labour by a Chadian court on Wednesday. But they are likely to have their sentences commuted into straight jail terms in France, where convicts cannot be required to carry out forced labour.

Francois Molins, the state prosecutor for the Paris suburb of Bobigny who met the charity workers at the airport, told a press conference that a decision is expected to be made by mid-January. “Some of them realise that they are entering a period that is going to be difficult,” he added.

Their arrival at 9pm at Le Bourget airport, north of Paris, ended the African chapter of a fiasco that has embarrassed the French authorities and most mainstream humanitarian organisations. There are suspicions in France that President Sarkozy, who infuriated authorities in N’djamena, the capital of Chad, when he promised to bring home the aid workers “whatever they’ve done”, may have been forced to offer some form of compensation to make good his pledge.

Antoine Glaser, director of La Lettre du Continent, a specialist African affairs journal, said that Idriss Déby, the President of Chad, had almost certainly received weapons in return for releasing the charity workers. The Chadian head of state needs arms to fight an insurgency, according to Mr Glaser. “My feeling is that a deal was done with Mr Sarkozy,” he said.

A French Justice Ministry official said that the six would almost certainly have to serve at least four years before being eligible for early release.

After a three-week hunger strike, the charity workers are described by their lawyers as weak. They will be interviewed by a prosecutor, who may authorise sending them to hospital.

Only two days after the trial ended in N’djamena, the six were flown back to France. They were accompanied by a doctor and eight members of the French prison service. Chadian officials said that they had also sent an observer to “verify that they serve their sentences in France”.

Although France has a 1976 judicial agreement with Chad to facilitate the repatriation of prisoners, the speed of the move will fuel accusations that the court hearing was a show trial designed to appease Chadian public opinion. Céline Lorenzon, a lawyer for Zoe’s Ark, described the case as a masquerade with its outcome determined in advance by President Déby after his negotiations with President Sarkozy.

Nonetheless, Eric Breteau, the founder of Zoe’s Ark, and the other five workers could face a separate prosecution in France, where they are under investigation on allegations of fraud, involvement in unlawful adoptions and planning illegal immigration. They face a maximum sentence of 15 years in prison if found guilty.

French commentators portray Zoe’s Ark as amateurish, naive and inexperienced rather than a criminal gang of child traffickers. Mr Breteau and his helpers were arrested in eastern Chad in October as they prepared to fly back to France with what they said were orphans from Darfur, the war-torn region of neighbouring Sudan.

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