The UK has carried out "serious human rights violations" as part of its war on terror, Amnesty International says.
Amnesty details alleged torture by UK troops in Iraq
The campaign group's annual report expressed concerns about alleged human rights abuses by UK troops in Iraq.
It also criticised the holding of 12 suspects under anti-terror laws without charge or trial.
The Foreign Office said all the Iraqi abuse claims were being investigated, while the Home Office said the holding of the suspects was necessary.
Hundreds of civilians had been killed and thousands injured by coalition bombing during the war in Iraq, the report said.
Thousands of people had been arrested and detained without charge or trial in Iraq, and "torture and ill-treatment by coalition forces were widespread", it said.
"Virtually none of the allegations of torture or ill-treatment was adequately investigated," Amnesty also claimed.
It detailed specific allegations of torture by British troops of nine men arrested working at a hotel in Basra, southern Iraq, where weapons had reportedly been found.
One of the men died in custody and a second was admitted to hospital in a critical condition, suffering renal failure and severe bruising, Amnesty said.
A Foreign Office spokesman said: "We take all the reports and allegations of abuse or breaches of human rights very seriously.
"All cases regarding allegations of abuse under UK responsibility have been or are being investigated."
She added that Amnesty's report failed to mention positive human rights developments in Iraq.
She highlighted the establishment of a ministry of human rights, that transitional law "effectively contains a bill of rights", and a "commitment to establishing a national human rights commission".
Amnesty's report also complained about the internment in the UK of 14 foreign nationals last year - two have since been freed - under the Anti-terrorism, Crime and Security Act.
Amnesty said appeals brought by 10 of the men between May and July 2003, "fell far short of international fair trial standards, including the right to the presumption of innocence, the right to a defence and the right to counsel".
"There was also grave concern at the reliance on secret evidence and at the executive's and judiciary's willingness to rely on evidence extracted under torture."
Protesters campaign for the release of detainees from Belmarsh jail
Amnesty added that the Act was "discriminatory" because only non-UK nationals could be interned.
A Home Office spokesman said: "Given the nature of the Home Secretary's assertion that these detainees are suspected international terrorists who could pose a threat to the national security of the UK, it is right they are held in a high security prison."
She said appeals by 13 of the detainees against their imprisonment had been rejected in all but one case.
She added that the powers granted by the Act had been "extensively debated by Parliament and we don't think it would be appropriate to reopen that debate".
"Human rights are for the best of us and the worst of us, for the guilty as well as the innocent," Amnesty Secretary General Irene Khan said.
"By failing to protect the rights of those who may be guilty, governments endanger the rights of those who are innocent, and put us all at risk."
The report also criticised jail conditions and collusion in Northern Ireland between "state agents and loyalist paramilitaries".