Edwards and Sato were worried the Foremans were being held for political leverage, and have appealed to the Iranian authorities to quash their convictions.
They urged the UK government to try all diplomatic means to get them freed. The couple’s last consular visit was back in December.
The Foreign Office said it would continue working to ensure that they are returned safely to the UK.
The couple recently lost an appeal against their 10-year sentence.
Lindsay’s son Joe Bennett, from Folkestone, Kent, said they were “not permitted to attend their own appeal hearing”.
Their case has now been passed to the Supreme Court, according to Bennett, although the family do not understand the legal process or the timeline of what might happen next.
Their last consular visit was back in December.
Joe, who has tirelessly campaigned for the couple’s freedom, previously said: “Deals can be made, sanctions can be discussed, shipping lanes can be reopened, but human beings must not be left behind in prison cells.
“My mum and Craig are British citizens. They are innocent people caught in a nightmare.
“Any serious peace framework with Iran must include the fate of foreign detainees.”
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