Anat Kam, 24, was convicted in February for copying 2,085 military documents on to a disc as she completed her mandatory army service and passing some of them to Uri Blau, an investigative reporter with the left-leaning Haaretz newspaper.

She escaped the much more serious charges of harming state security after reaching a plea bargain.

Her case provoked a domestic uproar – in part because she was held for four months under secret house arrest with the Israeli media banned from reporting on it, but also because it was viewed as an assault on the freedom of the press. The Independent was the first newspaper to report on Ms Kam's arrest.

In passing sentence yesterday, the three-judge panel elected to send a clear message to other would-be whistleblowers. "If the army cannot trust the soldiers serving in various units and exposed to sensitive issues, then it cannot function as a regular army," the judges wrote. They said that Ms Kam's motive for taking the documents was "mainly ideological". Ms Kam has already served nearly two years of house arrest, which will not count towards her prison term, and she received a further 18-month suspended sentence.

As a clerk in the Israeli Defence Forces' central command, Ms Kam stumbled across documents that appeared to point to the premeditated killing of Palestinian militants in the West Bank, despite a Supreme Court ruling that severely restricted such operations, determining that the army should arrest suspects if possible.

These documents formed the basis of Mr Blau's November 2008 story in which he questioned the army's claim that two Islamic Jihad militants killed in the West Bank the year before had died in an exchange of fire. He claimed that one of the two men had been identified months earlier by Israeli commanders as a target for assassination.

Over a year later, Ms Kam, by then a reporter at Walla!, a Hebrew web site, was quietly arrested. Although colleagues were aware of her fate, they were prevented from reporting on it because of a court gag order. As the story started to break internationally, frustrated Israeli journalists turned to increasingly inventive ways to tell the story at home, with one newspaper suggesting its readers google "Israeli journalist gag".

Mr Blau, meanwhile, had taken refuge in Britain. He later reached a plea bargain with Israel's security services, agreeing to return all of the classified documents in his possession, but could still reportedly face criminal charges.

Ms Kam's lawyer, Avigdor Feldman, slammed the sentence as too severe. That the army had allegedly violated a Supreme Court ruling "didn't get any attention by the government or the public", he told The Independent. "Instead it is Anat Kam being punished."