LONDON: Britain's Prime Minister Boris Johnson on Monday hit out at reports by British media and rights group Amnesty International that dual national Nazanin Zaghari-Ratcliffe had been sentenced to another year in prison in Tehran.

"I don't think it's right at all that Nazanin should be sentenced to any more time in jail... I think it's wrong that she's there in the first place," he said, adding that London was working "very hard" to secure her release.

Foreign Secretary Dominic Raab called the decision "totally inhumane and wholly unjustified".

British media reported that, in addition to the one-year prison sentence, she had been banned from leaving the country.

Zaghari-Ratcliffe appeared in court last month to face new charges of "propaganda against the system", a week after she finished serving a five-year sentence for plotting to overthrow the regime in Tehran -- accusations she strenuously denied.

She was initially detained while on holiday in 2016 while she was working as a project manager for the Thomson Reuters Foundation, the media organisation's philanthropic wing.

She has been under house arrest in recent months and had her ankle tag removed, giving her more freedom of movement and allowing her to visit relatives in Tehran.

Her husband, Richard Ratcliffe, and media in both the UK and Iran have drawn a possible link between Zaghari-Ratcliffe's detention and a British debt dating back more than 40 years for military tanks paid for by the shah.

When the shah was ousted in 1979, Britain refused to deliver the tanks to the new Islamic Republic and London has admitted it owes Iran several hundred million pounds.

Zaghari-Ratcliffe's constituency MP in London, Tulip Siddiq, said she was being "abusively used as a bargaining chip". But both London and Tehran have denied any link to her case.

While in prison, she suffered from a lack of hygiene and even contemplated suicide, according to her husband.

Richard Ratcliffe told AFP last month that he had hoped if convicted again, the time would be served under house arrest at her parents' house in Tehran.

"If she got put back in prison, regardless of the time, that's a really bad sign," he said, noting that it would clearly indicate negotiations between the British and Iranian governments had "fallen down".