LONDON (AFP) - Britain said on Thursday (March 7) it will grant "diplomatic protection" to Nazanin Zaghari-Ratcliffe, a UK-Iranian dual citizen jailed in Teheran since 2016, citing a lack of due process and access to medical treatment.
"I have today decided that the UK will take a step that is extremely unusual and exercise diplomatic protection," Foreign Secretary Jeremy Hunt said in a statement.
"This represents formal recognition by the British government that her treatment fails to meet Iran's obligations under international law and elevates it to a formal state to state issue."
Diplomatic protection is a rarely-used mechanism allowing nations to seek protection on behalf of its citizens on the grounds that they have been wronged by another state, according to Britain's foreign office.
Mr Hunt said he had "not taken this decision lightly" but considered the "unacceptable treatment" Zaghari-Ratcliffe had experienced during her three years in detention.
"We have not even been able to secure her the medical treatment she urgently needs despite assurances to the contrary," he added.
Zaghari-Ratcliffe has suffered from health issues, including undergoing tests for breast cancer and a series of panic attacks, while her emotional state has worsened during her confinement.
A project manager with the Thomson Reuters Foundation, the media group's philanthropic arm, she was arrested in April 2016 as she was leaving Iran after taking her infant daughter to visit her family.
She was sentenced to five years in prison in September 2016 for alleged sedition.
Zaghari-Ratcliffe, the Thomson Reuters Foundation and the British government have consistently denied the charges against her.
Mr Hunt said his decision on Thursday was "an important diplomatic step" signalling to Teheran that "its behaviour is totally wrong".
However he conceded that it was "unlikely to be a magic wand that leads to an overnight result" and repeated calls for her release.
"I know there are many in Iran who understand the unjustness of this situation. No government should use innocent individuals as pawns for diplomatic leverage so I call on Iran to release this innocent woman so she can be reunited with her family," he said.
Zaghari-Ratcliffe's husband Richard has been lobbying Mr Hunt and the previous foreign secretary Boris Johnson for diplomatic protection for his wife since 2017.