LONDON - British Foreign Secretary David Miliband branded as "wholly unjustified" Thursday a reported jail sentence handed to an embassy worker in Iran and urged Tehran authorities to overturn it.

British embassy worker Hossein Rassam was sentenced to four years in prison this week after being found guilty of fomenting violence during Iran's disputed presidential elections in June, The Times newspaper said.

A Foreign Office spokesman said their contacts in Iran confirmed the news, telling AFP: "We will wait for official confirmation but from our sources we understand that he has been sentenced."

Miliband said the sentence was further harassment of British embassy staff and described the "unacceptable Iranian action" as "deeply concerning."

"Reports that Hossein Rassam has been sentenced to four years in prison are deeply concerning," Miliband said in a statement.

"Such a decision is wholly unjustified and represents further harassment of embassy staff for going about their normal and legitimate duties."

He said Britain's ambassador in Tehran had spoken to the Iranian deputy foreign minister and contacts had been made with Iran's London envoy.

Rassam, the embassy's chief political analyst, was arrested along with eight other local employees of the embassy on charges of participating in the riots that followed the re-election of President Mahmoud Ahmadinejad.

The eight were later released but Rassam was put on trial along with an employee of the French embassy and a French lecturer.

"We understand the sentence can be appealed. I urge the authorities to conduct this quickly and overturn this harsh sentence," Miliband said.

"We are in close touch with EU and other international partners, who continue to show solidarity in the face of this unacceptable Iranian action," he added.

"This will be seen as an attack against the entire diplomatic community in Iran and important principles are at stake."

Diplomatic ties between Britain and Iran, already tense, have deteriorated since the election.

Iranian officials accused London of involvement in the post-election unrest, and the two countries expelled each other's diplomats in tit-for-tat moves in the aftermath of the street violence.

Dozens of people were killed and thousands arrested in the protests, which plunged Iran into its worst internal political crisis since the 1979 Islamic revolution.

Iran's supreme leader Ayatollah Ali Khamenei has pointed an accusing finger at London over the protests, describing it as the "most evil" of Iran's enemies. Britain has denied any involvement in the unrest.

Rassam was sentenced in a closed court room this week but the outcome has not yet been publicly announced in Iran, The Times said on its website.

Rassam is still on bail after his release from prison in August. It is unclear whether he will have to return to jail immediately or remain on bail pending his appeal, the newspaper said Thursday.