The husband of Nazanin Zaghari-Ratcliffe told the UK government not to act as a messenger for Iran's "mafia tactics" after he was urged to keep quiet in the weeks before her scheduled release.
Richard Ratcliffe spoke to officials on Friday to insist that the UK strongly backs the case for his wife's return to her family or risks being manipulated by the Islamic Revolutionary Guard Corps.
His comments have laid bare the continuing tensions between families of British detainees and the UK Foreign Office, which the former have repeatedly criticised for failing to secure the release of dual nationals from Iranian prisons.
In a note to the Foreign Office, Mr Ratcliffe said that the department had shown a "remarkable lack of judgment ... to allow itself to be enrolled in passing on IRGC threats to the family, and say it would be the fault of our campaigning around Nazanin’s release date if something happened to Nazanin or her family".
He rejected its advice to keep quiet before her scheduled release in March, writing on Twitter: "We continue to believe that transparency is the best form of protection from abuse.
"We have also made it clear the government’s role is to remind the Iranian authorities that Nazanin has the UK’s protection, not to act as a messenger for the Islamic Revolutionary Guard Corps' mafia tactics and suppression.”
Former foreign secretary Jeremy Hunt said that Ms Zaghari-Ratcliffe's voice must "never be silenced".
She is under house arrest at her parents’ home and next month is due to complete her five-year sentence after Iran claimed she plotted to overthrow the government.
Last year, Iran threatened to add more charges but the trial was delayed.
“If anything happens to Nazanin or her family or if she is not released to the UK on March 7, there should be consequences," Mr Ratcliffe wrote on Twitter.
"We will be discussing with the Foreign Secretary, Dominic Raab, his back-up plan.”
The Foreign Office believes quiet diplomacy has a greater chance of producing results and Mr Ratcliffe’s decision to make his wife’s detention a high-profile campaign has been a cause of tension.
After a meeting with diplomats on Friday, Mr Ratcliffe sent a note to the department.
“I said on the call that the UK government passing on this message ‘to inform our decision making’ was enabling Iranian mafia tactics. That is not an exaggeration," it read.
“We have discussed repeatedly the ways in which the IRGC have threatened the family, and attempted to manipulate them through insidious messages direct and through mediators.
“The IRGC have an infinite capacity to spot weakness and an opportunity to manipulate.
"It is why the UK’s weakness on diplomatic protection is so genuinely ill advised. They sniff out every opportunity, unless you push back immediately.”
Mr Ratcliffe is also pushing for his wife’s detention to be classified as “state hostage taking”.
“I don’t want there to be any doubt in the foreign secretary’s mind that we are approaching the time to make good on our conversations to impose a cost on hostage taking," he said.
"My view is that if you won’t do it now, even when Nazanin is not released at the end of her sentence, then it is safe to presume that you never will.
“Either she is home at the end of her sentence or there are consequences. Anything else is just noise.”
Last week, Iran’s judiciary spokesman Gholamhossein Esmaili warned Mr Raab not to interfere in Ms Zaghari-Ratcliffe’s case.
"Nazanin Zaghari is our current convict and she is serving her sentence, and she is yet to stand trial for another charge in her case that has been sent to the court with an indictment," Mr Esmaili said.