Former British resident Binyam Mohamed arrives back in Britain tomorrow after his release from Guantanamo Bay. British and US lawyers claim that sustained beatings - which have only recently stopped - have left him with severe psychological and physical problems. Defence correspondent Mark Townsend reports

Binyam Mohamed will return to Britain suffering from a huge range of injuries after being beaten by US guards right up to the point of his departure from Guantánamo Bay, according to the first detailed accounts of his treatment inside the camp.

Mohamed will arrive back tomorrow in the UK, where he was a British resident between 1984 and 2002. During medical examinations last week, doctors discovered injuries and ailments resulting from apparently brutal treatment in detention.

Mohamed was found to be suffering from bruising, organ damage, stomach complaints, malnutrition, sores to feet and hands, severe damage to ligaments as well as profound emotional and psychological problems which have been exacerbated by the refusal of Guantánamo's guards to give him counselling.

Mohamed's British lawyer, Clive Stafford Smith, said his client had been beaten "dozens" of times inside the notorious US camp in Cuba with the most recent abuse occurring during recent weeks. He said: "He has a list of physical ailments that cover two sheets of A4 paper. What Binyam has been through should have been left behind in the middle ages."

Lieutenant colonel Yvonne Bradley, Mohamed's US military attorney, added: "He has been severely beaten. Sometimes I don't like to think about it because my country is behind all this."

The former attorney general, Lord Goldsmith, who campaigned for Guantánamo Bay to be closed, said any allegation of US abuse against a British resident inside the prison should be urgently raised by the foreign secretary, David Miliband, with the US secretary of state, Hillary Clinton.

"If there are credible accounts of mistreatment then they need to be pursued," said Goldsmith.

Claims that Mohamed was beaten during the period after President Obama announced Guantánamo's closure in January risk harming diplomatic relations between the administration and the British government. Prime minister Gordon Brown is believed to have raised Mohamed's case with the US president during their first talk following Obama's inauguration two months ago.

Stafford Smith, the director of legal charity Reprieve, said yesterday that Mohamed had been routinely beaten by Guantánamo's notorious emergency reaction force, a six-strong team of guards in riot gear who have been the subject of previous abuse allegations. The alleged beatings were routinely administered against Mohamed "for no reason" and some were "recent" according to Stafford Smith.

Upon his return to England after more than four years inside Guantánamo, Mohamed will be taken to a secure, secret location in order for him to be fully rehabilitated by a team of volunteer doctors and psychiatrists. Mohamed will be kept under a "voluntary security arrangement" which involves reporting to the authorities, but he will not be subject to an anti-terror control order. His lawyers reiterate that he has nothing to hide after US terror charges against him were dropped last year.

Mohamed will not be debriefed upon his arrival by the British authorities or face any interview from the British security agencies. At least one MI5 officer is currently waiting to hear whether he will face a criminal investigation over alleged complicity in the torture of Mohamed, who settled in Kensington, west London, after arriving from Ethiopia as a teenage asylum seeker.

Mohamed's eventual testimony may also shed light on MI5's alleged complicity in his interrogation and alleged torture. One likely step will involve suing the British government and its security services over potential allegations of complicity in his illegal detention, abduction, treatment and interrogation.

Lord Carlile of Berriew, the independent reviewer of the anti-terrorism laws, warned yesterday that, once settled, Mohamed's possible legal action against the US or British authorities could force them to disclose vital evidence relating to the torture allegations.

Following his arrest in Pakistan more than six years ago, Mohamed has claimed he was told by British government officials that everything would be done to help him.

Lt Col Bradley, who is staying in England until Thursday to welcome Mohamed, said the most crucial issue was stabilising his health. Mohamed's weight has fallen from 170lbs to about 125lbs. "He needs to get his weight back on and start eating," she said.

Mohamed's return to England coincides with signs that the government is preparing to accept more detainees from Guantánamo in the face of increasing US pressure to help shut the camp.

The Foreign Office appears to be softening its stance towards accepting more detainees from the prison after last month insisting there were "no plans" to accept more inmates. The position has now shifted to a statement explaining that "no formal decision has been made" on the UK accepting detainees from other countries.

A Foreign Office source added that all cases were now being reviewed on an individual basis by the home secretary Jacqui Smith. This comes amid intensifying pressure from the US authorities, with the Observer learning that direct requests for Britain to accept more detainees have now been lodged by the Obama administration. Sources at the US department of defence said talks were ongoing with countries, including the UK, to re-house inmates.

Dean Boyd, spokesman for the US department of justice, said: "We will undoubtedly need the assistance of our close friends and allies as we work towards closing Guantánamo."

Goldsmith said Britain should accept prisoners from the camp if it would help Obama to close it down.

British citizens and residents mentioned in the report is Rangzieb Ahmed, 33, from Rochdale, who claims he was tortured by Pakistani intelligence agents before being questioned by two MI5 officers. Ahmed was convicted of being a member of al-Qaida at Manchester crown court, yet the jury was not told that three of the fingernails of his left hand had been removed. The response from MI5 to the allegations that it had colluded in Ahmed's torture were heard in camera, however, after the press and the public were excluded from the proceedings. Ahmed's description of the cell in which he claims he was tortured closely matches that where Salahuddin Amin, 33, from Luton, says he was tortured by ISI officers between interviews with MI5 officers.

Zeeshan Siddiqui, 25, from London, who was detained in Pakistan in 2005, also claims he was interviewed by British intelligence agents during a period in which he was tortured.

Other cases include that of a London medical student who was detained in Karachi and tortured after the July 2005 attacks in London. Another case involving Britons allegedly tortured in Pakistan and questioned by UK agents involves a British Hizb ut-Tahrir supporter.

Rashid Rauf, from Birmingham, was detained in Pakistan and questioned over suspected terrorist activity in 2006. He was reportedly killed after a US drone attack in Pakistan's tribal regions, though his body has never been found.

Hasan said: "What the research suggests is that these are not incidents involving one particular rogue officer or two, but rather an array of individuals involved over a period of several years.

"The issue is not just British complicity in the torture of British citizens, it is the issue of British complicity in the torture period. We know of at least 10 cases, but the complicity probably runs much deeper because it involves a series of terrorism suspects who are Pakistani. This is the heart of the matter.

"They are not the same individuals [MI5 officers] all the time. I know that the people who have gone to see Siddiqui in Peshawar are not the same people who have seen Ahmed in Rawalpindi."

Last night the government faced calls to clarify precisely its relationship with Pakistan's intelligence agencies, which are known to routinely use torture.

A Foreign Office spokesman said that an investigation by the British security services had revealed "there is nothing to suggest they have engaged in torture in Pakistan". He added: "Our policy is not to participate in, solicit, encourage or condone the use of torture, or inhumane or degrading treatment, for any purpose."

But former shadow home secretary David Davis said the claims from Pakistan served to "reinforce" allegations that UK authorities, at the very least, ignored Pakistani torture techniques.

"The British agencies can no longer pretend that 'Hear no evil, see no evil' is applicable in the modern world," he added.

Last week HRW submitted evidence to parliament's Joint Committee on Human Rights. The committee is to question Miliband and Jacqui Smith, the home secretary, over a legal loophole which appears to offer British intelligence officers immunity in the UK for any crimes committed overseas.

It has also emerged that New York-based HRW detailed its concerns in a letter to the UK government last October but has yet to receive a response.

The letter arrived at the same time that the Attorney General was tasked with deciding if Scotland Yard should begin a criminal investigation into British security agents' treatment of Binyam Mohamed. Crown prosecutors are currently weighing up the evidence.

Hasan said that evidence indicated a considerable number of UK officers were involved in interviewing terrorism suspects after they were allegedly tortured. He told the Observer: "We don't know who the individuals [British intelligence officers] were, but when you have different personnel coming in and behaving in a similar fashion it implies some level of systemic approach to the situation, rather than one eager beaver deciding it is absolutely fine for someone to be beaten or hung upside down."

He accused British intelligence officers of turning a blind eye as UK citizens endured torture at the hands of Pakistan's intelligence agencies.

"They [the British] have met the suspect ... and have conspicuously failed to notice that someone is in a state of high physical distress, showing signs of injury. If you are a secret service agent and fail to notice that their fingernails are missing, you ought to be fired."

Britain's former chief legal adviser, Lord Goldsmith, said that the Foreign Office would want to examine any British involvement in torture allegations very carefully and, if necessary, bring individuals "to book" to ensure such behaviour was "eradicated".