Government platitudes over the ongoing ordeal of the last British resident in Guantanamo are no longer enough, campaigners warned yesterday as damning new evidence of mistreatment emerged.

Shaker Aamer, from south London, has been detained at the US gulag since 2002 without charge or trial despite having twice been cleared for release by the US authorities.

During this time he has been subjected to appalling abuse and regular beatings.

The British government has repeatedly claimed that it has “raised” Mr Aamer’s case with the US and called for him to be returned to his family.

But Legal action charity Reprieve, which represents Mr Aamer, urged David Cameron to do more to secure his release during a two-day White House visit which began yesterday.

Reprieve has written to the Prime Minister informing him that “there are at least 315 instances in which Aamer has been videotaped while being beaten by the Forcible Cell Extraction squad at Guantanamo.”

The British government initially refused to ask the US about evidence of Mr Aamer’s abuse when Reprieve raised the issue with the Foreign Office last year.

Reprieve director Cori Crider said: “Shaker and his wife and four children in the UK have had enough of the tired old mantra from British officials that they have ‘raised the case’ with their US counterparts.

“The first statement to Parliament that Shaker’s case was ‘urgent’ was nearly two years ago. No more excuses. Platitudes about ‘raising Shaker’s case’ are just not enough anymore.”

A group of senior doctors has also called for Mr Aamer to be released, warning of his “fragile medical condition.”

The medics said that Mr Aamer was suffering from conditions including post-traumatic stress disorder and asthma and that his continued detention was having an “appalling effect” on his health and that of his family.

In a letter to the Daily Mail the group, including consultants and professors, said Mr Aamer had “pressing medical concerns.”

Signatories include three members of the Foreign Office pro bono medical panel, which can assist with advice for Britons held overseas but which the doctors said had so far not been allowed to help Mr Aamer.