The husband of the jailed Iranian dual national Nazanin Zaghari-Ratcliffe has criticised Donald Trump’s killing of the Iranian general Qassem Suleimani, saying it is hard to demand Iran complies with the rule of law if its adversaries play fast and loose with the same law.

Richard Ratcliffe again urged Boris Johnson, the British prime minister, to find time to meet him to discuss his wife’s plight.

He also said the near-collapse in relations between the west and Iran made it more difficult to convince his wife that her release from Evrin jail in Tehran may be imminent.

Zaghari-Ratcliffe has been detained since 2016 after she was arrested on espionage charges and jailed for five years.

Ratcliffe, speaking on BBC Radio 4’s Today programme, said his wife and other British and Americans citizens were being held as collateral and the last few day’s events made it much harder to secure release any time soon.

He said: “We are held by the [Revolutionary Guards] and obviously they have lost their leader. More broadly, part of our campaigning has been to call on Iran to uphold the international law and to respect UN rulings in Nazanin’s case, and that gets a bit harder when international law is played fast and loose with by other parties.”

Profile Who was Qassem Suleimani? Show Qassem Suleimani, killed by a US drone strike in Baghdad, had become well known among Iranians and was sometimes discussed as a future president. Many considered Suleimani to have been the second most powerful person in Iran, behind supreme leader of Iran Ali Khamenei, but arguably ahead of President Hassan Rouhani. He was commander of the Quds Force, the elite, external wing of the Iran’s Islamic Revolutionary Guard Corps, which the Trump administration designated as a terror organisation in April last year. He was born in Rabor, a city in eastern Iran, and forced to travel to a neighbouring city at age 13 and work to pay his father’s debts to the government of the Shah. By the time the monarch fell in 1979, Suleimani was committed to the clerical rule of Ayatollah Ruhollah Khomeini, and joined the Revolutionary Guards, the paramilitary force established to prevent a coup against the newly declared Islamic Republic. Within two years, he was sent to the front to fight in the war against the invading Iraqi army. He quickly distinguished himself, especially for daring reconnaissance missions behind Iraqi lines, and the war also gave him his first contact with foreign militias of the kind he would wield to devastating effect in the decades to come. By the the time the Iraq government fell in 2003, Suleimani was the head of the Quds force and blamed for sponsoring the Shia militias who killed thousands of civilian Iraqis and coalition troops. As fighting raged on Iraq’s streets, Suleimani fought a shadow war with the US for leverage over the new Iraqi leadership. Once described by American commander David Petraeus as ‘a truly evil figure’, Suleimani was instrumental in crushing street protests in Iran in 2009. In recent months outbreaks of popular dissent in Lebanon, Iraq and Iran were again putting pressure on the crescent of influence he had spent the past two decades building. Violent crackdowns on the protests in Baghdad were blamed on militias under his influence.

Eighteen months before his death, Suleimani had issued Donald Trump a public warning, wagging his finger and dressed in olive fatigues. “You will start the war but we will end it.” Michael Safi Photograph: Mehdi Ghasemi/AFP

He said Johnson must argue that Trump’s policy on Iran needed to be “an awful lot clearer strategically in protecting people”.

His comments came as the wife of a British-Iranian engineer in prison in Tehran told how she feared for his safety in the wake of Suleimani’s assasination and pleaded with Johnson to redouble his efforts to help negotiate the release of her husband.

Sherry Izadi said her husband, Anoosheh Ashoori, who was jailed for 10 years in August on disputed espionage charges, and other dual nationals being held in prison had previously been threatened by guards who said they would machine-gun them.

Izadi spoke to her 65-year-old husband, who is also held in Evin prison, on Sunday morning and said he was “very concerned” by reports of two British warships being sent to the region.

Asked if she had a message for the prime minister, Izadi told Sky News: “I would like to tell him to please do everything possible to get him out, especially in view of the recent situation because sometimes … it doesn’t feel safe where they are.

“A couple of occasions, some guards had told, not just my husband, but a couple of other dual nationals, that ‘we don’t really see why they keep you alive here, you’re all a bunch of spies, you’re a bunch of traitors and if it were up to us, some of us, we would just take a machine gun and kill you all’.

“But, obviously you know, they’re not allowed. But when something like this happens, when a major figure, heroic figure in Iran, like Suleimani, is killed, obviously the backlash is immediately on the people that they perceive to be sympathetic to his killers, which includes US, which includes the UK.

“So I really would like the prime minister to double, to treble his efforts. Please do something.”

Izadi said there had yet to be any direct repercussions on her husband’s treatment following Suleimani’s death, but added: “Obviously everyone is really concerned, especially the dual nationals there because they’re afraid of reprisals and we’re just waiting to see how it will go.”

Ashoori, who had lived in the UK on and off since the age of 17, was arrested in 2017 while visiting his mother in Iran. He was convicted last year of being an Israeli spy, a claim his family have dismissed as “laughable”.

A petition set up by his wife to campaign for his release has attracted more than 50,000 signatures.

Meanwhile, the former British foreign secretary Jeremy Hunt said there was a risk of escalation through “unintended consequences”.

Asked on BBC One’s Breakfast programme if the killing of Suleimani had been a good idea, Hunt said: “Only time will tell the answer to that question. But what we have at the moment is a very dangerous, tinderbox situation. Both sides are underestimating the strength and resolve on the other side.”

He added: “That is the real danger that we face at the moment – that risk of unintended consequences. Because neither side wants a war, I don’t think there will be a war, but both sides will feel the need to retaliate when they are attacked.”

It was, Hunt said, “very regrettable” that the UK and other European nations had not been consulted in advance about the plan. The US-Europe alliance had become “a lot more tatty in recent years”, in part due to disparities in defence spending, he said.

“From the American standpoint, they’re asking themselves, just how relevant is Europe, because they don’t think we’re putting our money where our mouth is.”

