Britain said on Friday it was sending Iran a "very strong message" by extending diplomatic protection to a British-Iranian mother jailed in Tehran in a move that was
immediately branded by the Islamic republic as a violation of international law.
The fate of Nazanin Zaghari-Ratcliffe has been a bone of contention between Tehran and London since her arrest in Iran in January 2016.
The 41-year-old was returning from a family visit with her infant daughter when she was detained at Tehran airport by security agents who recorded her arrest on video.
That footage was played on Iranian television in December as the case gained new political dimensions in both London and Tehran.
Her husband Richard said Zaghari-Ratcliffe suffers from a range of health problems that forced her to go on a brief hunger strike in January to protest a lack of medical access in jail.
"I think it's a really important step. It's a clear and strong signal that Nazanin is supported by the British government and is innocent," Richard Ratcliffe told AFP.
UK Foreign Secretary Jeremy Hunt said that London's decision to offer Zaghari-Ratcliffe diplomatic protection "hasn't happened for an individual, we donât think, for more than 100 years".
"It sends a very strong message to Iran," Hunt told BBC radio.
"At the heart of this is an innocent woman, vulnerable, unwell and scared and she has a four year old daughter," he said.
"She should not be paying the price for the disagreements you have with the UK."
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.
But Iran quickly stated the London decision was a violation of international law.
"UK Govt's extension of diplomatic protection to Ms Zaghari contravenes int'l law. Govts may only exercise such protection for own nationals," Tehran's London envoy Hamid Baeidinejad tweeted late Thursday.
"As UK Govt is acutely aware, Iran does not recognize dual nationality. Irrespective of UK residency, Ms Zaghari thus remains Iranian," he wrote.
- 'A great day' -
Hunt said London wanted to make Iran aware that it had no intention of letting Zaghari-Ratcliffe languish in jail.
"We hope the Iranians will react constructively to this and understand that we are not going to drop this. We are treating this very, very seriously," he said.
Zaghari-Ratcliffe was a project manager with the Thomson Reuters Foundation -- the media group's philanthropic arm -- and made frequent visits to Iran.
But she was on a personal holiday and not a work assignment at the time of her arrest.
She was sentenced to five years in prison in September 2016 for allegedly trying to topple the Iranian government.
The Thomson Reuters Foundation and the British government have also consistently denied the charges against her.
Richard Ratcliffe told reporters in January that the Iranian authorities were trying to make Zaghari-Ratcliffe spy on the British government for them, once she is released from jail.
He said she had refused to cooperate and had since been feeling "very low".
"She was taken for an initial assessment to a doctor, who said she was surprised she was in prison given the health condition she was in. So she's obviously not in a great position," he told BBC radio on Friday.
But he said Hunt's decision to grant Zaghari-Ratcliffe diplomatic protection filled him with hope.
"It's a great day that the foreign secretary has finally done it and I really appreciate it," Ratcliffe said.
"Now it is effectively a British government case. All the injustices that have been done to Nazanin are effectively injustices to the British government."afp