The French charity workers arrested on a mission that they claimed was to rescue orphans in Darfur, were last night told that they would be charged with kidnapping.

A prosecutor in Chad said that the six workers along with three French journalists accompanying them would face charges of abduction and fraud. They could be jailed for 20 years if found guilty, according to the French press.

Seven crew members of the Spanish charter plane that was to fly them to France and two Chadians will be charged with aiding and abetting.

Ahmat Daoud, the prosecutor in Abéché, eastern Chad, said: “For the nine French people it is a matter of kidnapping of minors . . . as well as extortion.” They are likely to be transferred to a prison in N’djamena, the capital of Chad, during the investigation.

The Belgian pilot of their charter plane, who has also been arrested, is likely to learn today whether he will be prosecuted.

Zoe’s Ark, a small charity based near Paris, insisted that its only aim had been to bring orphans out of Darfur, the war-ravaged region of Sudan, and fly them to foster care in France. “The team is made up of firemen, doctors and journalists,” said Christophe Letien, the charity’s spokesman. “It’s unimaginable that doubts are being cast on these people of good faith who volunteered to save children from Darfur.”

Maître Gilbert Collard, a lawyer for for Zoe’s Ark, said: “We are dealing with humanitarian hardliners who went off the beaten track. They wanted to do things differently – that doesn’t mean that they wanted to do it dishonestly.”

The workers were detained near the Sudanese border last week as they prepared to fly 103 children to Rheims in eastern France, where foster families were waiting for them.

Idriss Déby, the Chadian President, has accused Zoe’s Ark of “kidnap, pure and simple”. Mr Déby has suggested that the charity intended to hand the children over to paedophiles or kill them and sell their organs – although neither allegation appears to have been substantiated by an investigation in France.

“These foster families are not paedophiles. An exaggeration like that only shows how far this affair has turned political,” Maître Collard said.

Annette Rehrl, a spokeswoman for the UN High Commissioner for Refugees, said few of the children appeared to have been orphaned. “They keep saying that they want to return to their parents. Most of them are between three and six years old. It’s very difficult to ask three-year-olds their names and where they come from. Also, some children have already changed their names and stories,” she said.

On Sunday, the children told reporters that they were from Chad and had been lured away from home with sweets and biscuits. Yesterday, however, one of the boys claimed that he was from Sudan. “That’s not true, he’s Chadian,” said a social worker at the foster home where the children are staying.

The incident has fuelled fears in Paris that the fiasco is being exploited by Chadian authorities to whip up antiFrench sentiment as the European Union prepares to send a peacekeeping force to protect refugees along the border between Chad and Sudan. Mr Déby accepted the 4,000-strong force, which will include an important French contingent, with reluctance and may want to use Zoe’s Ark as a bargaining chip to reduce its scope.

As Paris sought to prevent the affair from turning into a diplomatic row, Mr Déby assured Nicolas Sarkozy, the French President, that he would not seek to block the EU troops.

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