With another jailed British dual-national confined to solitary confinement, Nazanin Zaghari-Ratcliffe committed to a New Year’s Eve hunger strike in solidarity with her compatriot and a Frenchwoman in the same situation.

West Hampstead's Nazanin spent Christmas Eve on strike in a show of support for Dr Kylie Moore-Gilbert, who has been held alone in Evin Prison for nine months and who was given a ten-year prison sentence last week.

As this newspaper went to press, Nazanin had confirmed she and a number of others would be on hunger strike with Dr Moore-Gilbert and Dr Fariba Adelkhah.

Nazanin's husband Richard said: "It is so that their strike does not pass unnoticed. They already did a day on Christmas Eve, so that Kylie would not be alone. And I think they all feel this really has to end. The PM has done enough sunning himself while this goes on."

In an open letter published by supporters of Dr Moore-Gilbert and Dr Adelkhah, and confirmed by the Centre for International Research at Sciences-Po where Dr Adelkhah works, the two women said: "We will strike on behalf of all academics and researchers across Iran and the Middle East, who like us have been unjustly imprisoned on trumped up charges and simply doing their job as researchers.

"We have been subjected to psychological torture and numerous violations of our basic human rights."

But Iranian Foreign Ministry spokesman Seyyed Abbas Mousavi said Ms Moore-Gilbert, who holds dual British and Australian citizenship, is being afforded her legal rights.

He said: "She has been arrested on a charge of violating Iran's national security, and the competent court has also issued the appropriate ruling by observing all relevant laws.

"Experience has shown that the Islamic Republic of Iran would not give in to the political and smear campaigns, and this Australian citizen is serving her sentence while enjoying all legal rights, like any other convict with a judicial verdict."

Earlier, Richard had told in the Guardian urged the British Government to "shake off the complacency of their holiday heads" as his wife prepares to enter 2020 on hunger strike.