ES News email The latest headlines in your inbox twice a day Monday - Friday plus breaking news updates Enter your email address Continue Please enter an email address Email address is invalid Fill out this field Email address is invalid You already have an account. Please log in Register with your social account or click here to log in I would like to receive lunchtime headlines Monday - Friday plus breaking news alerts, by email Update newsletter preferences

Authorities in Iran have cancelled Nazanin Zaghari-Ratcliffe's weekly call with her husband after the announcement that she will begin a hunger strike this month.

The British-Iranian mother jailed in Tehran is set to start the three-day strike mid-January after being refused access to medical help.

On Sunday, organisation Free Nazanin said Iranian authorities have cancelled Mrs Zaghari-Ratcliffe's scheduled call with her husband Richard Ratcliffe and imposed restrictions on all other calls.

Mr Ratcliffe said last week she was to embark on a hunger strike 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.

Mr 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".

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.

Free Nazanin tweeted on Sunday: "Following announcement of a planned hunger strike, Iranian authorities have cancelled Nazanin’s weekly call with her husband and imposed restrictions on all other calls."

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.

Tulip Siddiq, Labour MP for Ms Zaghari-Ratcliffe's constituency, tweeted: "Heartbreaking news that Nazanin’s right to call her family and husband is now being restricted.

"My constituent has suffered enough and our Gov’t must stop this attempt to cut her off from the outside world.

Additional reporting by Press Association.