Craig and Linsday Foreman had entered Iran despite Foreign Office advice – which warns against travelling to the country due to the risk of being arrested – but with valid visas, a tour guide and a pre-approved itinerary.
The couple had been on a “once in a lifetime” motorbike journey from Europe to Australia and had only intended to be in Iran for a few days.
Linsday Foreman, a life coach, had been asking people along the route what it means to live a good life.
They were both given 10-year sentences last month, after a “sham trial”, according to their family.
Foreign Secretary Yvette Cooper described the sentences at the time as “completely appalling and totally unjustified”.
She met Mr Bennett to discuss the case last week, but he expressed frustration afterwards, saying the government lacked a clear strategy or sense of urgency.
“While France and Germany have secured the release of their citizens through assertive intervention, the UK remains trapped in a wait-and-see approach that has already cost my parents nearly 15 months of their lives,” he said.
The Foreign Office’s website advice on not travelling to Iran states: “Having a British passport or connections to the UK can be reason enough for the Iranian authorities to detain you.”