The husband of a British charity worker jailed in Iran has warned his wife is on “a precipice” and at risk of suicide, after making the decision to send her daughter home to London for school, depriving her of weekly visits.

The only communication Nazanin Zaghari-Ratcliffe, 40, will have with her daughter Gabriella, five, once she returns to the UK, is five-minute phone calls if and when prison guards permit it. Gabriella was 22-months-old when her mother was arrested by Iran’s infamous Revolutionary Guards at Tehran airport in April 2016 while they were both on holiday in the country.

When Ms Zaghari-Ratcliffe was sentenced to five years in jail on spying charges, Gabriella remained in Iran, visiting her mother in prison once a week for the last few years. The Iranian-British dual national, who has staged several hunger strikes, had hoped to return home with her daughter. But with little movement in her case, she was forced to make the agonising choice of letting her daughter go home for school.

Ms Zaghari-Ratcliffe released a heartfelt plea for her freedom from jail on Thursday saying: “I am a desolate mother ready to burn like a desert dune”.

Mr Ratcliffe, who has not seen either his wife or daughter since the spring of 2016, said he feared for his wife as Gabriella “is her lifeline”.

Nazanin Zaghari-Ratcliffe – in pictures Show all 20 1 /20 Nazanin Zaghari-Ratcliffe – in pictures Nazanin Zaghari-Ratcliffe – in pictures 2018 Nazanin Zaghari-Ratcliffe hugs her daughter Gabriella, in Iran after she was allowed to leave the Iranian prison, she is being held in, for three days. Zaghari-Ratcliffe was arrested during a holiday with her toddler daughter in April 2016. Iranian authorities accuse her of plotting against the government. Her family denies this, saying says she was in Iran to visit family. Free Nazanin Campaign/AP Nazanin Zaghari-Ratcliffe – in pictures Nazanin Zaghari-Ratcliffe with her husband Richard Ratcliffe and their daughter Gabriella. Nazanin is serving a five-year prison sentence for allegedly plotting to overthrow Iran's government. PA Nazanin Zaghari-Ratcliffe – in pictures June 2016 Richard Ratcliffe's daughter Gabriella had her British passport confiscated and was stranded in Iran with her grandparents after her mother Nazanin was jailed. He left left a giant birthday card on the doorstep of the Iranian embassy in central London to mark her second birthday in June 2016. PA Nazanin Zaghari-Ratcliffe – in pictures Nazanin has spent some of her prison sentence in solitary confinement. PA Nazanin Zaghari-Ratcliffe – in pictures Nazanin Zaghari-Ratcliffe with her husband Richard and daughter Gabriella. Family Handout Nazanin Zaghari-Ratcliffe – in pictures July 2016 Richard Ratcliffe delivering a letter of petition with his mother Barbara Ratcliffe and MP Tulip Siddiq, to 10, Downing Street on the 100th day of her detention, on July 12, 2016. Getty Nazanin Zaghari-Ratcliffe – in pictures Supporters of Nazanin Zaghari-Ratcliffe held a vigil outside the Foreign and Commonwealth Office to mark her 707 days in captivity. Getty Nazanin Zaghari-Ratcliffe – in pictures January 2017 Richard Ratcliffe holds a '#Free Nazanin' sign and candle during a vigil for for wife on January 16, 2017. The vigil, being held outside the Iranian Embassy in London marks one year since the Washington Post journalist Jason Rezaian and other US-Iranian dual-nationals were released from prison in Iran. Getty Nazanin Zaghari-Ratcliffe – in pictures Nazanin with her daughter Gabriella before they were detained by Iranian authorities. Change.org Nazanin Zaghari-Ratcliffe – in pictures September 2017 Gabriella, who is three-years-old in this picture, has now spent two years away from her mother. Richard Ratcliffe Nazanin Zaghari-Ratcliffe – in pictures November 2017 Foreign Secretary Boris Johnson meets with Richard Ratcliffe over Nazanin's case. They meet just days after Johnson told a parliamentary committee that she was in Iran "training journalists". WPA Pool/Getty Nazanin Zaghari-Ratcliffe – in pictures November 2017 Actor Emma Thompson braved pneumonia to support Richard Ratcliffe in leading demonstrators before a march in support of Nazanin in November. Reuters Nazanin Zaghari-Ratcliffe – in pictures November 2017 Richard Ratcliffe after the march said: 'It is profoundly moving to see so many people here.' REUTERS Nazanin Zaghari-Ratcliffe – in pictures November 2017 A picture of Nazanin Zaghari-Ratcliffe shown on Iranian state TV as part of a report that made fresh allegations against her. They said she had been recruiting for banned broadcast services, as well as 'opposition cyber teams'. Nazanin Zaghari-Ratcliffe – in pictures December 2017 Iranian president Hassan Rouhani greets British Foreign Secretary Boris Johnson at the presidential office in Tehran, Iran. Johnson visited Tehran to discuss the fate of detained Nazanin Zaghari-Ratcliffe. EPA Nazanin Zaghari-Ratcliffe – in pictures Nazanin Zaghari-Ratcliffe with her daughter Gabriella. PA Nazanin Zaghari-Ratcliffe – in pictures December 2017 Photos of Richard Ratcliffe and his wife Nazanin Zaghari-Ratcliffe on display at their home in north London. Mr Ratcliffe said he believed there was "still a chance" she may be released from an Iranian prison in time for a dream Christmas together. Unfortunately that didn't happen. PA Nazanin Zaghari-Ratcliffe – in pictures February 2018 Richard Ratcliffe delivers a petition and a letter addressed to the Iranian Deputy Foreign Minister Abbas Araghchi to demand her release, at the Iranian Embassy in London on February 21, 2018. He also left support letters for his spouse in the country's embassy, amid a visit by a deputy foreign minister. AFP/Getty Nazanin Zaghari-Ratcliffe – in pictures August 2018 Foreign Secretary, Jeremy Hunt meeting Richard Ratcliffe. Hunt has pledged to do everything possible to secure the release of a charity worker jailed in Iran Jeremy Hunt/PA Nazanin Zaghari-Ratcliffe – in pictures August 2018 Nazanin Zaghari-Ratcliffe hugs her daughter Gabriella, in Iran after she was allowed to leave the Iranian prison, she is being held in, for three days. Zaghari-Ratcliffe was arrested during a holiday with her toddler daughter in April 2016. Iranian authorities accuse her of plotting against the government. Her family denies this, saying says she was in Iran to visit family. PA

“We are all on a precipice. It is bleak, she cannot go on much longer. Her reserves of hope are depleting,” he told The Independent. “We fear she will take things into her own hands. If we are lucky it will be a more militant hunger strike, if not she may attempt suicide.”

He said he was concerned that Gabriella will find it hard to re-adjust to life in the UK. Mr Ratcliffe is unable to speak to his daughter without a translator as she has been in Iran for so long.

“She doesn’t really know her daddy that well anymore, she doesn’t really know London. She can’t speak English,” he continued.

“We have been separated for so long. I’m a rusty parent”.

“The Foreign Office needs to be more assertive with Iran on these cases, there needs to be a cost for hostage-taking,” he said.

Ms Zaghari-Ratcliffe, who worked for the Thomson Reuters Foundation, the charitable arm of the news agency, was visiting her parents in Tehran when she was arrested while trying to board a plane home. She was held for months in solitary confinement and later sentenced to five years in jail on espionage charges, after a short trial panned by human rights groups as unjust.

Her family believes she is being held as political leverage in a dispute between Iran and the British government. Over the summer, she went on another hunger strike in protest of her continued detention.

The Iranian authorities responded by chaining her to a bed in a psychiatric unit and briefly banning phone calls to her husband or visits from her daughter. With little hope of a speedy release, she eventually decided to send her daughter back to London.

In a letter smuggled out of her jail cell and addressed to “the mothers of Iran”, she wrote that separation from her daughter is the “deepest torture of them all”.

“I have no hope or motivation after my baby goes. There is no measure to my pain,” she said.

“It is such a bitter feeling to know you are stuck unjustly in prison in your own country, with no road to freedom ahead. I am a desolate mother ready to burn like a desert dune when her baby leaves.”

She is one of dozens of dual nationals who are currently behind bars in Tehran’s infamous Evin Prison. In August, Iranian judicial officials reported that Anousheh Ashouri, a British-Iranian dual national, was sentenced to 10 years in prison, again on spying charges.

Richard Ratcliffe says his wife had been chained to a bed in solitary confinement (EPA)

A few weeks later, the Iranians arrested two British-Australian women, Kylie Moore-Gilbert, a Middle East politics specialist at Melbourne University, and travel blogger Jolie King, together with Mark Firkin, an Australian man – on unknown charges.

In July, more than 200 MPs called for Boris Johnson to use his powers to secure Mrs Zaghari-Ratcliffe’s safe release from Iran. He is under pressure to secure her release after inadvertently worsening her situation when in 2017 he said she was in Iran “teaching people journalism”.