A BRITISH-IRANIAN mother detained in Tehran is to embark on a hunger strike as a "last resort" over being denied health care, her husband said.

Nazanin Zaghari-Ratcliffe, whose sister-in-law is a GP in Cwmbran, will strike for three days in mid-January with Narges Mohammadi, an Iranian human rights defender who is also behind bars in Evin prison.

Mrs Zaghari-Ratcliffe has suffered a catalogue of mental and physical health complaints since she was arrested at Tehran's Imam Khomeini airport on April 3, 2016.

Her husband Richard Ratcliffe said his wife was having medical treatment blocked for checking lumps in her breasts, neurological care over her neck pains and numbness in her arms and legs, and for seeing an outside psychiatrist.

He said her requests for treatment were being blocked "despite having been approved by the prison doctor".

He told the Press Association: "I think it's a real last resort step, and I did not think we were at last resorts just yet."

He added: "In fairness to her, I have been campaigning for a long time, and we will continue campaigning, but I can't sit back and tell her that it's worked because she's still in prison."

If the pair are not granted the specialist care they seek, they will continue to refuse food, they said in a joint letter, warning Iran's authorities that they will be held responsible for the potential consequences.

The open letter was initially published in Farsi by the Defenders of Human Rights Centre.

Their translation into English said the pair's "repeated requests" for medical treatment had been rejected.

It continued: "Therefore, in protest to this illegal, inhuman and unlawful behaviour, and to express our concerns for our health and survival at this denial of specialist treatment, despite taking daily medicines, we will go on hunger strike from 14.01.2019 to 16.01.2019.

"We are urging for an immediate action to be taken.

"We announce that in the event of the authorities' failure to address these concerns and them further endangering our health, we will take further actions.

"The authorities of the Islamic Republic of Iran are to be held responsible for the potential consequences."

Mrs Zaghari-Ratcliffe, a charity worker of Hampstead in north London, was sentenced to five years in jail after being accused of spying, a charge she strongly denies.

The British-Iranian mother spent her 40th birthday on Boxing Day in prison, where she has been detained for more than 1,000 days.

Mr Ratcliffe said his wife was concerned that time was running out to give her daughter, four-year-old Gabriella, a sibling.

He said: "In terms of her wanting to have a second child, I fear that might be stolen.

"For her it's been looming for a long time. Not only have we not been able to watch Gabriella grow up, we might not get to have another baby. She feels it viscerally."

He has requested an urgent meeting with Iran's UK ambassador and will next speak to his wife on Sunday.

Foreign secretary Jeremy Hunt wrote on Twitter: "Nazanin is innocent and must be allowed to come home.

"How can the Iranian authorities allow an innocent mother to feel she needs to resort to this, simply for justice and access to medical care?"

Lulip Siddiq, Labour MP for Ms Zaghari-Ratcliffe's constituency, tweeted: "Nazanin has again been driven to despair because of the hopelessness of her plight.

"The cruelty of her captors + our Government's failure to secure release means her life is at risk. What is the PM's plan to bring her home? Quiet diplomacy has failed."

Ellie Kennedy, an individuals at risk campaigner at Amnesty International UK, said: "It should obviously never have come to this.

"The Iranian authorities are entirely responsible for pushing these two unfairly-detained people to take such desperate measures.

"It's shocking and unforgivable that the Iranian authorities can callously force prisoners of conscience into starving themselves in protest at their plight, and they should immediately provide full medical care to Nazanin and Narges."