The foreign secretary, Jeremy Hunt, has accused Iran of using Nazanin Zaghari-Ratcliffe, who has been imprisoned for 1,000 days, as a pawn for diplomatic leverage.

Zaghari-Ratcliffe, a British-Iranian dual national from Hampstead, north London, has been held in Iran since April 2016. Tehran, which accused her of seeking to overthrow the government, has ignored repeated calls from her family and UK officials to release her.

Speaking on BBC’s Radio 4’s Today programme on Friday, Hunt said: “Nazanin isn’t the only person who is being detained, despite being totally innocent, as a pawn of diplomatic leverage.

“On Boxing Day, Nazanin was 40 years old and she has been imprisoned for more than half of her four-year-old daughter’s life. This is monstrous, it is totally unjust.”

Zaghari-Ratcliffe was working for the Thomson Reuters Foundation when she was arrested at Imam Khomeini airport in Tehran in 2016 and later sentenced to five years in jail for spying, a charge she vehemently denies.

In a video message released this week, Richard Ratcliffe, her husband, pointed out that 28 December would be his wife’s 1,000th day in prison. He said she had spent her 40th birthday, which fell on Boxing Day, in jail.

Hunt added: “Iran is a country which has a great civilisation behind it. One of the oldest civilisations in the world. They want to be respected by other countries. This is not the way to do it – to imprison an innocent woman like this – and I really hope they will think again.

“We have diplomatic differences with many countries across the world, but we don’t have other countries who lock up innocent people as a tool of diplomatic leverage, and it has to stop.”

The Foreign Office was sharply criticised earlier this year by Daniela Tejada, whose husband, Matthew Hedges, was detained for seven months in the United Arab Emirates after he was accused of being a British spy.

After accusing Hunt’s department of putting relations with the Gulf state before her husband’s freedom, he reached out to Tejada to reassure her.

“I spoke to her after she made those comments and I explained to her that I’d actually raised the issue four times with the highest authorities in the UAE. And I think she heard that,” Hunt told Today.

“I accept there was probably a misunderstanding in some of the communication that she had with some people in London. I think the key thing here is that Matthew Hedges was given a life sentence, we did everything we could to get him out and we succeeded.”