Craig and Lindsay Foreman were arrested in January, but news of their detention, on unspecified security charges, only emerged earlier this week.

The couple, both aged 52, had been on a motorbike trip across the world and had only planned to be in Iran for five days.

Mr Ratcliffe, whose wife was arrested in Iran in 2016 and not released until six years later, said the dangers of travelling to the country would be “a lot clearer” if Foreign Office travel advice reflected “the risks of hostage-taking” there.

The UK Foreign Office advises against all travel to Iran, saying British and British-Iranian dual nationals are at “significant risk of arrest, questioning or detention”.

Having a British passport or connections to the UK “can be reason enough for the Iranian authorities to detain you”, it adds.

The Foreman family said the couple’s detention was a “distressing situation” and they are “deeply focused on ensuring their safety and wellbeing during this trying time”.

Responding to the case, Mr Ratcliffe told the PA news agency: “My heart goes out to them, and I hope they are not in for a long ordeal, and that the government is able to respond more promptly than it did in our case.

“I do think the risks would be a lot clearer to people if the UK travel advice to Iran talked about the risks of hostage-taking. People would be more alert to the fact that it is not personal, and it doesn’t matter whether you have travelled there with a good heart.”

Posting on Instagram before being detained, Mrs Foreman acknowledged travelling to Iran, against Foreign Office advice, and to Pakistan was risky and “slightly scary”.

But she wrote “we know the rewards of meeting incredible people, hearing their stories, and seeing the breathtaking landscapes of these regions could far outweigh the fear”.

Mr Ratcliffe said the “top priority” for the UK government should be ensuring Mr and Mrs Foreman were not being held in solitary confinement, because it was “important they do not feel alone”.

He added a court process in the case may happen soon but said: “It’s not a real court… it will be a form of brutal theatre to get the government’s attention. And it will hurt much the same. I really hope they will be okay.”

The UK Foreign Office did not respond directly to Mr Ratcliffe’s comments when approached by BBC News, but said it was providing consular assistance to two British nationals detained in Iran and is in contact with the local authorities.

Ms Zaghari-Ratcliffe, a British-Iranian national, was arrested at an airport in Tehran in April 2016 and accused of spying charges, which she denied.

Mr Ratcliffe went on hunger strike twice as part of his campaign for his wife’s release.

She was ultimately freed and returned to Britain in March 2022 after the UK government agreed to settle a £400m debt dating back to the 1970s.

Mr and Mrs Foreman were heading for Australia on their journey across the globe and had crossed into Iran from Armenia on 30 December. They planned to be in Pakistan by 4 January.

After staying in the cities of Tabriz, Tehran and Isfahan, accompanied by a tour guide, they travelled on to Kerman, in east-central Iran, but never checked into their hotel there.

The Iranian authorities have not said what the couple are accused of.

In a series of social media posts before they were detained, the pair described their joy at being in Iran.

Mrs Foreman, a life coach with a doctorate in psychology, said she was “having an amazing time”. Her husband Craig, who is a carpenter, spoke of the “lovely people” of a “lovely country”.

The couple had moved from East Sussex to start a new life in Andalucia, Spain, in 2019 and appeared on an episode of Channel 4’s A New Life in the Sun in 2022 to showcase their lives as expats.

Mrs Foreman is reported to have been carrying out a research project on their journey to Australia, asking people what it means to be human and what constitutes a good life.

She was due to present her findings at a conference on positive psychology in Brisbane in July.