The American journalist Roxana Saberi was jailed for espionage in Tehran after obtaining a confidential Iranian document about the American invasion of Iraq, it was claimed today.

Saleh Nikbakht, one of Ms Saberi's Iranian lawyers, revealed that a document Ms Saberi had obtained while working as a translator for a powerful clerical lobby had been used as evidence to convict her on charges of espionage.

Ms Saberi, 32, was released on Monday after an appeal court dismissed charges of spying and reduced her eight-year prison term to a two-year suspended sentence.

Abdolsamad Khorramshahi, the lead defence counsel, said that she had “accepted that she had made a mistake and got access to documents she should not have".

However, no classified information had been passed on, he added.

Ms Saberi apologised for keeping the document, and the court reduced the charge against her from espionage to possessing confidential documents.

Ms Saberi obtained the document that was used in her conviction while she was working as a freelance translator for the Expediency Council, a powerful body in Iran’s ruling clerical hierarchy.

The council’s role is to mediate between the legislature, presidency and ruling clerics in constitutional disputes.

Her release ends a three-month diplomatic stand-off between Tehran and Washington that had threatened to derail President Obama’s efforts at rapprochement.

Last month, President Ahmadinejad intervened to steer the case towards appeal, judging the public mood to be in favour of warmer relations. Mr Ahmadinejad faces an election early next month against a reformist, pro-Western rival.

In her first public appearance after walking free from three months in prison, Ms Saberi avoided any comment on the machinations surrounding her arrest and subsequent release.

Looking thinner after a two-week hunger strike following her conviction, Ms Saberi emerged from her apartment building in Tehran to address reporters and to pay thanks to those who had worked for her release.

“I’m very happy to be released and to be with my father and mother again,” she said. “I’m thanking all those people around the world who knew me or who didn’t know me but helped my release. Right now I just want to be with my parents and my friends and to rest a little bit.”

Ms Saberi’s Iranian-born father, Reza, who has been in Tehran lobbying for her release, said that the appeal court had accepted she had made statements under pressure, and had pleaded guilty in the hope of release before retracting.

Her original conviction was also on charges of working with a “hostile country” – the United States. The court dismissed that charge on the grounds that the US is not a hostile country because it is not at war with Iran.

In her court appearance on Sunday, Ms Saberi admitted that she possessed the document. She had said that she copied it out of curiosity, but had not passed it to American officials, Mr Nikbakht said.

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