Channel 4 News has learned a British Somali man imprisoned in the US for alleged terrorism has gone on hunger strike and is now in a "critical condition", according to his family.

Mahdi Hashi

Mahdi Hashi was born in Somalia and grew up in Camden, north London, after his family moved to Britain when he was five, writes Fatima Manji.

The former community worker was controversially stripped of his British citizenship last year after being accused of fighting with al-Shabaab extremists in Somalia.

The 24-year-old now faces the possibility of life in an American jail, without any support from his former home country.

For more than four weeks, Hashi has been on hunger strike, saying his body is all he has left to protest with. In a short phone call to his father on Thursday night he said doctors are now treating him for jaundice, but he remains determined not to eat. Mahdi's family are growing increasingly fearful over his condition.

The FBI accuses Mahdi of fighting with militant group al-Shabaab in Somalia. It says he took part in weapons training and al-Shabaab's suicide bombing programme. But Mahdi and his family deny the charges and say he moved to Somalia to start a new life after being harassed by British security services.

I caught up with Mahdi's father Mohammad Hashi, who still lives here in London.

Trying to recruit

Mohammad Hashi says his son used to work for a community youth group called the Kentish Town Youth Workers, around five years ago. At the time, he says MI5 was constantly trying to recruit him and his friends. Mohammad says at times he was present, when MI5 agents were trying to call his son and that his son "was sick of it".

In 2009, Mahdi complained to his local MP, Frank Dobson. Mr Dobson confirms he received a complaint from this group and took it to the Home Office, because he was concerned about the methods being employed by the security services against a group he believes were "doing good work to combat extremism and help Somali kids" in the area.

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But according to Mahdi's family the complaints made no difference and as Mahdi kept receiving calls, he decided to leave the UK and begin a new life in Somalia.

Then in summer last year, his family received a letter from the Home Office saying Mahdi was being stripped of his citizenship for being involved in terrorist activity.

The letter came as a shock to the Hashi family. They called Mahdi to tell him the news and urged him to go to the nearest British embassy to appeal.

But shortly afterwards Mahdi vanished. His family were unable to make contact with him and appealed to the Foreign Office to help, but as Mahdi was no longer a British citizen - no help was received.

'Not involved'

Six months later, the family suddenly found out Mahdi was in prison in New York awaiting trial. The FBI released a statement in December 2012 saying Mahdi was one of three men "apprehended in Africa by local authorities while on their way to Yemen" and had been charged in a "sealed court".

It alleges Mahdi was "deployed in combat operations to support al-Shabaab action in Somalia".

Mohammad Hashi says he is confident his son was not involved with al-Shabaab or any other terrorist group while in Somalia. He says Mahdi was staying with his grandmother and he himself visited the house, stayed with him for a month and had not "come across any suspicious things".

He also believes Mahdi was tortured before being renditioned to the US. The FBI told Channel 4 News it has nothing further to add at this stage.

The Hashi family are now appealing against the decision to strip his British citizenship, here in the UK. The Home Office says it can't comment on the case while this is ongoing.

But as Mahdi remains on hunger strike with little access to his legal team in the UK, his father fears his son stands little chance of being able to make his case.