BORIS Johnson is expected to call Iran's foreign minister on Tuesday morning following reports that comments he made were being used in Tehran as a justification to extend the jail sentence imposed on a British woman.

The Foreign Secretary is facing calls to retract his claim to a parliamentary committee last week that Nazanin Zaghari-Ratcliffe was training journalists in Iran at the time of her arrest last year, something her employer and her family insist is incorrect.

Richard Ratcliffe, Zaghari-Ratcliffe's husband said Johnson should make a statement in Parliament to correct his mistake in an effort to prevent the sentence being lengthened.

And shadow foreign secretary Emily Thornberry said Johnson should quit if his actions have damaged Zaghari-Ratcliffe's prospects of freedom.

In a statement released by the Foreign Office, a spokesman did not offer any correction, saying instead that Johnson's comments may have been "misrepresented" and they provide "no justifiable basis" for additional charges.

Zaghari-Ratcliffe, who is serving a five-year sentence in an Iranian jail, was summoned to an unscheduled court hearing last weekend at which Johnson's remarks were cited as proof that she had been engaged in "propaganda against the regime".

Reports suggest the new charge could add five years to her prison term, imposed over unspecified allegations of involvement in a supposed coup attempt against the Tehran regime, which she denies.

Ratcliffe told BBC Radio 4's Today programme that a public retraction by Johnson was required.

"I would like him to retract in Parliament, in Parliament rather than in a phone call to his counterpart, what he said, and say clearly that Nazanin wasn't training journalists and that she was just there on holiday."

He also called on Johnson to visit Zaghari-Ratcliffe in prison but insisted he remained hopeful his family could be reunited within weeks.

"I have promised Nazanin that it's still possible that they will be home for Christmas.

"I'm still battling on those terms."

In a letter to the Foreign Secretary, Thornberry said that, although Johnson's comment was not a deliberate error, it "reveals a fundamental lack of interest or concern for the details of Nazanin's case and the consequences of your words".

She told Johnson: "In the event that your actions have indeed cause irreparable harm to Nazanin's prospects of freedom and result in her sentence being lengthened, I hope and trust that you will take full responsibility for that, in both a moral and political sense, and consider your position accordingly."

Zaghari-Ratcliffe insisted in her original trial that she was not working in Iran at the time of her arrest, but was visiting the country to show her infant daughter Gabriella to her grandparents.

Johnson told a parliamentary committee on November 1: "When I look at what Nazanin Zaghari-Ratcliffe was doing, she was simply teaching people journalism, as I understand it.

"(Neither) Nazanin Zaghari-Ratcliffe nor her family has been informed about what crime she has actually committed.

"And that I find extraordinary, incredible."

Following Saturday's hearing, the Iranian judiciary's High Council for Human Rights said: "His statement shows that Nazanin had visited the country for anything but a holiday.

"For months it was claimed that Nazanin is a British-Iranian charity worker who went to see her family when she was arrested ... Mr Johnson's statement has shed new light on the realities about Nazanin."

Zaghari-Ratcliffe's employer, Thomson Reuters Foundation, urged Johnson to correct his "serious mistake".

A Foreign Office spokesman said: "Last week's remarks by the Foreign Secretary provide no justifiable basis on which to bring any additional charges against Nazanin Zaghari-Ratcliffe.

"While criticising the Iranian case against Mrs Zaghari-Ratcliffe, the Foreign Secretary sought to explain that even the most extreme set of unproven Iranian allegations against her were insufficient reason for her detention and treatment.

"The UK will continue to do all it can to secure her release on humanitarian grounds and the Foreign Secretary will be calling the Iranian foreign minister to raise again his serious concerns about the case and ensure his remarks are not misrepresented."