"That is no way acceptable," said the spokesman, Ramin Mehmandoust.

"The insistence of the French authorities on presenting unjustifiable demands and questioning Iranian jurisdiction threatens to create unfavourable conditions that could harm the Iranian judiciary's confidence in the sincerity of French officials about the undertakings given by the French embassy.

"Clotilde Reiss will not be pardoned under political pressure and nobody has the right to decide on the judge's behalf," the spokesman added.

French Foreign Minister Bernard Kouchner said on Tuesday that Clotilde Reiss would not turn up in court unless she received assurances that she could stay in the embassy pending a verdict in her trial on charges of "provoking rioters" during the protests that followed Iran's disputed June presidential election.

"She will go with certain guarantees," Kouchner said. "She must be able to leave the courthouse in Tehran and return to the embassy."

Le Figaro newspaper last week reported the embassy had sent a formal letter to the Iranian foreign ministry requesting assurances that her release on bail in August would not be overturned.

Reiss had planned to fly home after completing a six-month teaching and research assignment in the central city of Isfahan. In the closing weeks of her stay she witnessed the protests, took pictures and emailed them to friends.

Scores of reformists, journalists and opposition supporters were jailed following the mass protests over hardline President Mahmoud Ahmadinejad's re-election, and more than 140 have appeared in mass trials.

France has insisted that Reiss is not guilty and has demanded her unconditional release.

Tehran's chief prosecutor said on Monday that the trial of the 24-year-old Iran specialist would resume following her first court appearance on August 8 on charges of "collecting information and provoking rioters."

Tensions between Tehran and Paris over the strong line the French government has taken over the Iranian nuclear programme have clouded the case.