The British-Iranian woman serving a five-year jail sentence in Tehran for alleged sedition will appear in court on December 10 charged with spreading propaganda, her husband said Thursday.

Nazanin Zaghari-Ratcliffe, who works for the Thomson Reuters Foundation (TRF) -- the media organisation's philanthropic arm -- was told about the court date by the country's deputy prosecutor yesterday, Richard Ratcliffe said.

The new charge could result in a further lengthy sentence.

The case has become highly politicised in Britain after Foreign Secretary Boris Johnson was accused of jeopardising Zaghari-Ratcliffe's defence.

He told a parliamentary committee earlier this month that she had been training journalists in Iran before she was arrested -- a comment her employer and her family said was wrong.

Ratcliffe met with Johnson last week to lobby for his wife to get diplomatic protection, and for him to accompany the foreign secretary on an upcoming visit to Tehran.

The requests were under review, the foreign office said afterwards.

Zaghari-Ratcliffe was arrested at Tehran airport on April 3, 2016 after visiting relatives in the country with her young daughter.

Iran's elite Revolutionary Guards accused her of having taken part in the "sedition movement" of protests that followed the disputed 2009 re-election of then hardline president Mahmoud Ahmadinejad.

She was sentenced to five years in jail, before authorities last month presented extra charges.

After being held in solitary confinement, she has been transferred to the women's quarters of Evin Prison in Tehran, where she has received visits from her daughter, who is living with grandparents in Iran after her passport was confiscated.

Ratcliffe will attend a march on Saturday in the family's home neighbourhood of West Hampstead in London, alongside local resident and Oscar-winning actress Emma Thompson, who will lead calls for Zaghari-Ratcliffe's release.

Meanwhile, an online petition for her release has collected more than 1.3 million signatures.

Ratcliffe also revealed Thursday that his wife has not developed breast cancer as recently feared.

She had discovered lumps on her breast, and was examined in a Tehran hospital in recent weeks.

However, the lumps responded to prescribed medication, indicating they are not cancerous, he told British media