A British man jailed in Iran after being accused of spying has had two years added to his decade-long sentence, according to family members.

Craig Foreman was arrested with his wife, Lindsay, in January last year while passing through Iran on a motorcycle journey from Europe to Australia. Both adamantly deny espionage.

In February they were each sentenced to 10 years in jail, but relatives of Craig Foreman said he had been told his punishment is being extended for talking to the media from his cell in Tehran’s Evin prison.

The Foreign, Commonwealth & Development Office (FCDO) said the department was “urgently following up with the Iranian authorities about the reported increased sentence”.

“We understand he was told he was being taken to see his lawyer but was instead brought before a judge and informed of the additional sentence,” said Joe Bennett, Lindsay Foreman’s son and a spokesperson for the family.

Bennett, of Folkestone, Kent, added that, despite requests, his step-father “was allowed no lawyer, no translator and no opportunity to defend himself”.

“We didn’t think we could be any more shocked at their appalling treatment, but in this case we are absolutely flabbergasted,” he added.

Craig and Lindsay Foreman, from East Sussex, have both been on hunger strike since May, when prison authorities prevented them from calling their families.

The family, who are growing increasingly concerned for their health, are now appealing to the Iranian authorities to show mercy, and set them free.