Comedian Frankie Boyle has started a hunger strike in support of Guantánamo Bay prisoner Shaker Aamer.

Mr Aamer, of Battersea, has been imprisoned since February 2002 without trial or even being charged by the US authorities since he was captured in Afghanistan in November 2001.

He has been on hunger strike for 150 days, with Mr Boyle and Aamer's lawyer Clive Stafford Smith joining him in solidarity.

Reports from his US lawyer suggest the situation has become so precarious prison authorities are force-feeding him to prevent starvation.

Mr Boyle began fasting on Thursday, while Smith has been participating in the challenge for seven days.

He has been posting tweets on his experiences, earlier joking: "Well Day 1 of hunger not too bad. But let's remember who's really suffering. My local pizza shop. I jest. Have a read."

Yesterday he wrote: "Day 2 of hunger strike feels a bit like being drunk.

"Feel pretty good, but no doubt I'll wake up to find myself in bathroom eating soap."

In May campaigners also began a hunger strike to support Mr Aamer and held a vigil outside Parliament.

A total of 96 prisoners in the detention centre are believed to be on strike, out of the 166 held.

Boyle donated £50,000 compensation from a libel case against the Daily Mirror to Mr Aamer's legal fund last year.