Nazanin Zaghari-Ratcliffe is to go on hunger strike in solidarity with another dual national being held in Iran.

Kylie Moore-Gilbert, a British-Australian academic, started an open-ended hunger strike six days ago in protest at being sentenced to 10 years on espionage charges. She wants at minimum to be moved from solitary confinement.

She has been held in solitary since October 2018. Just before Christmas she wrote to the Australian prime minister, Scott Morrison, pleading for ministers to do more to secure her release.

A spokesman for Iran’s foreign ministry, Abbas Mousavi, rejected the flurry of publicity over her case and said Iran would not submit to political games or propaganda.

The British-Iranian Zaghari-Ratcliffe and many other imprisoned dual nationals in Tehran believe they are being held as political hostages. Zaghari-Ratcliffe has already undertaken one hunger strike in solidarity with Moore-Gilbert and has said she will start another before New Year’s Eve. Zaghari-Ratcliffe was jailed four years ago.

A third dual national, Fariba Adelkhah, a French-Iranian academic, is also on hunger strike. The French government has summoned the Iranian ambassador over her detention.

Zaghari-Ratcliffe’s husband, Richard Ratcliffe, said of Moore-Gilbert’s plight: “Five days on dry hunger strike is becoming critical, and our thoughts go out to Kylie and her family for all this ordeal.

“She was already being taken to the health clinic after 48 hours. By now I would expect Kylieand Fariba to be there almost permanently. If it continues as planned they only have days.

“It gives some sense of just how desperate 16 months in solitary makes you. At some point you really feel you have nothing left to get noticed, nothing left to lose.

“I hope the Australian and British governments also step up today and shake off the complacency of their holiday heads. It is one thing for the Iranian regime to hold innocent people hostage, it is quite another to let them die.”

In her latest letter to the Australian government, Moore-Gilbert said: “Over the past nine months I have been completely banned from any contact with my family, with the exception of a three-minute phone call (all with my father), which was only granted after I took desperate measures which put my own life at risk.

“I have undertaken five hunger strikes as my only means to raise my voice, but to no avail. As predicted, I have now received a conviction of 10 years in prison, and my appeal court has failed.”

She urged the Australian ministers to review what they had been doing to secure her release.

The Iranian government says both academics were found guilty of espionage and that any interference by foreign governments will not help their case.

Mousavi said: “The statement by France’s foreign ministry regarding an Iranian national is an act of interference and we see their request to have no legal basis.

“The individual in question [Adelkhah] is an Iranian national and has been arrested over acts of espionage.”

He said her lawyer had knowledge about the details of the case, which was being investigated.

Iran does not recognise dual nationality and has repeatedly rebuffed calls from foreign governments for consular access to those it has detained.