Four British men held at the Guantanamo Bay prison camp for nearly three years are suing the US government.
Detainees at Guantanamo Bay are from around 40 countries, says the Pentagon
The ex-detainees are alleging torture and other human rights violations.
In the first action of its kind, Shafiq Rasul, Asif Iqbal, Rhuhel Ahmed and Jamal al-Harith each demanded £5.5m, in the suits filed in Washington DC.
But a Pentagon official said the allegations were false and the men were not entitled to a pay out because they had been captured in combat.
Among the defendants named are US Defence Secretary Donald Rumsfeld and chairman of the Joint Chiefs of Staff General Richard Myers.
The former detainees - three from Tipton in the West Midlands and Mr al-Harith, 37, from Manchester - filed the suits in Washington DC on Wednesday.
The men were released from the US naval base in Cuba in March.
They claim they were subjected to beatings and abuse during their "arbitrary" detention at Guantanamo Bay prison camp.
After they were freed, all the men were questioned by British police but released without charge.
The lawsuits were filed in Washington by the men's lawyers at Baach Robinson and Lewis.
The action is being brought under the Alien Tort Claims Act, Geneva Conventions, and Religious Freedom Restoration Act, according to a statement from the Center for Constitutional Rights.
The New York-based centre is supporting the four men.
The four former detainees are seeking damages but primarily want Rumsfeld and other defendants to be
held accountable for their actions, said Eric Lewis, the lead lawyer in the case.
"This is a case about preserving an American ideal - the
rule of law," Lewis said at a news conference.
"It is un-American to torture people. It is un-American to hold people indefinitely without access to counsel, courts or family. It is un-American to flout international treaty obligations."
In response, a Pentagon official said: "The allegations of torture are false. But the Department of Defence will not comment on specific details.
"Under US law, there is no basis to pay claims to individuals captured during combat.
"The four were captured in Afghanistan while fighting illegally for al-Qaeda.
"They were detained as a result of their activities in Afghanistan."
If the case proceeds, it will be heard in the Federal District Court in Washington DC.
The suit also names Maj. Gen. Geoffrey Miller, former commander at Guantanamo Bay base, as well as
other named officials and up to 100 "John Does" who allegedly were "involved in the illegal torture of plaintiffs" at the camp.
Dossier of 'abuse'
In August, Mr Ahmed, 22, Mr Rasul, 27, and Mr Iqbal, 22, accused the US of a catalogue of shocking abuses in a 115-page dossier.
The 'Tipton Three' alleged that they were beaten, stripped, shackled and deprived of sleep during their detention.
It was alleged that guards threw prisoners' Korans into toilets and attempted to force them to give up their religious faith.
There were claims that detainees were forcibly injected with unidentified drugs and intimidated with unmuzzled dogs.
The three men each said they eventually gave false confessions that they appeared in a video with al-Qaeda leader Osama bin Laden and Mohammed Atta, one of the September 11 hijackers.
They said this was despite the fact they could prove they were in Britain when the video was made.