Bennett said that no evidence of spying has ever been presented by the Iranian authorities.

He said the UK government must “act decisively and use every available avenue” to bring them home.

The family say a judge delivered the sentence at the Branch 15 of the Tehran Revolutionary Court.

The Sussex couple, who are both in their 50s, had endured 13 months in “dire” conditions, Bennett has previously said – adding that they were surrounded by “dirt, vermin, and violence”.

He said they had not been eating and were losing weight.

The Foremans are detained in separate wings in Tehran’s notorious Evin prison, which has long drawn criticism for alleged torture and inhumane conditions. It reportedly holds thousands of inmates, including journalists and political prisoners.

Bennett has said the couple’s lawyers in Iran made it clear there was no legal basis for a case against them. He added that their bail applications had been ignored.

Bennett has said that his mother and stepfather’s plight left him with “sick with worry” and that he has repeatedly pressed the Foreign, Commonwealth & Development Office (FCDO) to help them.

He has said that his family felt “abandoned” by the government, and that letters he sent to the prime minister and foreign secretary have gone unanswered.

The FCDO has previously said it was “deeply concerned” by the Foremans’ situation and that it continued to raise their case “directly” with Iranian authorities.

French citizens Cécile Kohler, Jacques Paris and Olivier Grondeau, and German national Nahid Taghavi, were all released from Iranian jails following sustained pressure by their respective governments, their families said.

The BBC was previously told that the couple may be being used as bargaining chips between Iran and its Western opponents, and that it was hoped a deal could be brokered as Trump attempts to improve relations with Iran.

On Tuesday, Iran said it had found “grounding principles” with the US to resolve disputes over its nuclear programme.

The meeting took place after the US made repeated military threats over Iran’s deadly crackdown on anti-government protests.

Activists say that at least 6,000 people were killed in the demonstrations against the government and high living costs. Thousands more deaths are being investigated.