A British-Iranian woman being held in Iran has been told she can either keep her two-year-old daughter with her in prison or give up custody.

Nazanin Zaghari-Ratcliffe is behind bars for allegedly plotting to topple the government in Tehran.

In a recent phone conversation, she told husband Richard Ratcliffe that Revolutionary Guard officials said she must choose between having her daughter, Gabriella, stay with her in Tehran's Evin prison for up to three days a week, or sign a document saying she does not want the "right to be with her young daughter".

Mrs Zaghari-Ratcliffe told her husband both options were unacceptable.

According to Amnesty International UK, Evin prison authorities imposed the choice in an attempt to counter negative publicity caused by the 37-year-old being separated from her toddler.

The charity worker is said to have suffered a serious decline in her physical and mental health since being convicted on unspecified "national security charges" and given a five-year jail sentence in September.

Mrs Zaghari-Ratcliffe, from Hampstead, north-west London, was arrested at Tehran Airport on April 3 with Gabriella.

Kathy Voss, Amnesty International UK's Individuals At Risk campaign manager, said: "This is yet another turn of the screw for Nazanin.

"What kind of refined cruelty is it that would involve presenting a mother with a 'choice' to either jail her own daughter or give her up entirely?

"The Iranian authorities should release Nazanin and end this cruel charade of justice immediately. Meanwhile, up until she's released, Nazanin should be allowed extended contact with her daughter.

"All along the Iranian authorities appear to have been playing politics with this case. We need to see the UK Government stepping up its efforts to unlock things politically and see that Nazanin is released as soon as possible."