Nazanin Zaghari-Ratcliffe's husband has admitted he "resented" Boris Johnson's handling of her case during his tenure as Foreign Secretary.
Richard Ratcliffe has joined his wife in staging a hunger strike against her detention in Iran over spying allegations, which she denies.
Speaking on Sunday outside the Iranian embassy in London, where he is holding his demonstration, Mr Ratcliffe said the goal is to "amplify her message" and provoke a response from Iran.
He reiterated criticism for Tory leadership frontrunner Mr Johnson's previous comments about the case.
"He clearly made a mistake and clearly tried to correct it and made a promise that he wasn't able to deliver on," Mr Ratcliffe told the Andrew Marr Show.
"At times I've resented him for it and there are bits I did resent him for."
Mr Johnson said in 2017 that Mrs Zaghari-Ratcliffe was working in Tehran training journalists, comments used by Iran to allege she was engaged in "propaganda against the regime".
Mr Ratcliffe added Mr Johnson "probably got over-criticised for some things, under-criticised for some things".
The family will now "push" Foreign Secretary Jeremy Hunt, another Tory leadership hopeful, for his wife's release, he said.
Mr Hunt has urged Iran to release Mrs Zaghari-Ratcliffe and not "drag her into" its disagreements with Britain.
She started her new hunger strike in prison on Saturday and her husband said his job "is to keep going as long as she goes if I can".
The couple have a five-year-old daughter, Gabriella, who has not been allowed to leave Iran following her mother's arrest in 2016 and is living with her grandparents.
"We are both parents to Gabriella and obviously it's important that this doesn't go to the bitter end," Mr Ratcliffe said.
"The message from Nazanin of course is that enough is enough and I think she wanted to make it clear to the authorities in prison that this can't go on."
He admitted he does not believe the Iranian authorities will concede.
"I had a chat with the Foreign Secretary yesterday, it felt like there were sort of mixed signals coming out of Iran," he said.
Mrs Zaghari-Ratcliffe's detention is now also against a backdrop of heightened tensions over an attack against two oil tankers in the Gulf of Oman.
"There's always been a backdrop of things that are tough and you're right that the oil tanker seems to have escalated quite a lot, so we're always worried," Mr Ratcliffe added.