By Michael Holden and Elizabeth Piper
LONDON (Reuters) - British Prime Minister Theresa May's government is considering granting diplomatic protection to a jailed aid worker in Iran as part of an effort to secure her release from a jail in the Islamic Republic.
Nazanin Zaghari-Ratcliffe, a project manager with the Thomson Reuters Foundation, was sentenced to five years after being convicted by an Iranian court of plotting to overthrow the clerical establishment. She denies the charges.
Her husband, Richard Ratcliffe, said the case had become a bargaining chip for Iran in its relations with Britain and urged Foreign Secretary Boris Johnson to extend diplomatic protection for his wife.
It is unclear how such protection could be offered retrospectively to a dual Iranian-British citizen, or whether such a move would secure her release, but May's spokesman said that it was one option being considered.
"I think that the foreign secretary has obviously spoken with her husband and that is one of the options being looked at," the spokesman said.
"The prime minister has been involved with this case from the outset, she's raised it with the Iranian president on at least two occasions, the entire government is working towards securing her release as quickly as possible."
A legal opinion prepared for human rights charity Redress on Zaghari-Ratcliffe's case said the British government could grant her diplomatic protection as she is "predominantly" a British citizen who has been denied a fair trial.
It is unclear how Tehran would view such a step which would explicitly make Zaghari-Ratcliffe's fate an issue in state-to-state relations rather than a purely consular case.
Zaghari-Ratcliffe's fate become a major political issue in Britain after Johnson said on Nov. 1 that she had been teaching people journalism before her arrest in April 2016, contradicting statements from her employer.
The Thomson Reuters Foundation, a charity organization which is independent of Thomson Reuters and which operates independently of Reuters News, said she had been on holiday and had not been teaching journalism in Iran.
Iranian state television said Johnson's comments showed Zaghari-Ratcliffe's guilt and that she was involved in spying.
Johnson later said his remarks could have been clearer and there was no doubt she had been on holiday, although opposition Labour Party leader Jeremy Corbyn said he should resign.
Her husband said it would not be helpful for Johnson to resign but asked to come with Johnson on a trip to Tehran planned for later this year.
"Nazanin is being held because she is British and is being used as a bargaining chip against the UK, now justified by your words," he said in an article in the Evening Standard newspaper.
"Nazanin is no longer simply a consular case as she has been endangered in a deeper way," he wrote.
The situation had affected his wife's health, he said, saying she had gone to hospital for tests after finding lumps on her breasts, which the specialist thought were benign and stress-related.
Opposition lawmakers have called on Johnson to resign for his remarks which they say have endangered Zaghari-Ratcliffe.
British ministers have rallied round Johnson but one of his allies, Environment Secretary Michael Gove, was accused of muddying the waters in a television interview on Sunday when he said he did not know what Zaghari-Ratcliffe was doing in Iran.
(Editing by Guy Faulconbridge and Angus MacSwan)