Torture is never acceptable and evidence extracted under torture should never be admissible in UK courts, except in proceedings against the alleged torturer, said Amnesty International today (17 October) as the UK Law Lords began their considerations on the issue.

Lawyers representing Amnesty International and 13 organizations will be in court from today asking the Law Lords to overturn a 2004 judgment by the Court of Appeal of England and Wales permitting the admissibility of torture evidence from abroad in domestic proceedings.

"The UK must not accept the unacceptable. Torture is abhorrent and can never be condoned under any circumstances. It is banned under international law and with good reason – there is no place for torture anywhere in the world," Amnesty International said.

"This is a momentous case. The UK is at an important crossroad. It can reaffirm its stand against torture, which is absolutely banned, or slide towards illegality by its tacit acceptance that torture is 'sometimes OK'. If it takes the latter path it will provide a cloak of legality for that which is unlawful."

The Court of Appeal ruled in August last year that evidence obtained by torture of a third party abroad would be admissible in proceedings before the Special Immigration Appeals Commission providing the torture was not committed or connived at by UK agents.

In the intervention to the UK's highest Court, Keir Starmer, QC representing Amnesty International and the other 13 organizations, will underscore the fact that under international law - which the UK cannot unilaterally change - torture is absolutely prohibited in all circumstances.

Amnesty International also warned of the dangerous precedent that would be set, should the Law Lords fail to rule against torture evidence.

"Failing to rule out the use of any torture evidence in UK proceedings would give a green light to torturers the world over. Rather than leading the way in the fight against this vile practice, the UK would legitimize the actions of torturers and provide a cloak of legality for their abhorrent and unlawful practice," Amnesty International said.

In its submission to the Law Lords, Amnesty International has joined forces with 13 other national and international organizations which have extensive experience in working to eradicate the use of torture: the Advice Centre on Individual Rights in Europe (The AIRE CENTRE), the Association for the Prevention of Torture, British Irish Rights Watch, The Committee on the Administration of Justice, Doctors for Human Rights, Human Rights Watch, The International Federation of Human Rights, INTERIGHTS, The Law Society of England and Wales, Liberty, the Medical Foundation for the Care of Victims of Torture, REDRESS and the World Organisation Against Torture.

The organizations are represented in this case, pro bono, by Keir Starmer, QC, Mark Henderson, Joseph Middleton, Peter Morris, Laura Dubinsky all of Doughty Street Chambers and Richard Stein, Jamie Beagent and Jo Hickman of Leigh and Day Solicitors.

Amnesty International concluded: "Let us be clear what we are talking about. This is not about whether evidence is useful. This is about whether the UK will turn a blind eye to someone being thrown in a cell and having pain and terror inflicted upon them."

"International law is clear; it tells states: don’t torture people; don’t send anyone to a country where they would risk being tortured; and don't use evidence extracted under torture in proceedings except in those against torturers. Having already sought ‘Diplomatic Assurances’ with states known to torture in the hopes of returning people to places where they would face risk of torture, the UK is now in danger of heading down a slippery slope towards failing on two of these three counts."

• Close Guantánamo Bay: shut down the detention camp, charge the detainees under US law in US courts or release them.

Set up on a US naval base on the island of Cuba, Guantánamo Bay was designed as an attempt to put detainees beyond the reach of the rule of law – any law whether US or international. The US Supreme Court ruled that challenges to detention could be brought in the US courts, but not a single case of a Guantánamo detainee has been reviewed by a US court - the US government continues, so far successfully, to block any such reviews. The detention camp at Guantánamo Bay has become the site and symbol of failure to respect human rights in the “war on terror”, and the call for its closure a rallying cry for those demanding respect for human rights and the rule of law.

The US government’s preferred option, if there is to be trial of detainees at all, is trial by military commissions. The commissions do not comply with international standards of fairness. They can impose the death penalty, are not independent of the executive and can admit secret evidence, and evidence obtained under torture or other coercion. There are severe restrictions on the rights to choose a lawyer and to mount an effective defence, and no right of appeal from them to the courts. They are discriminatory, only non US nationals can be tried.

The “Combatant Status Review Tribunals” which determine the status of Guantánamo detainees rely on similarly flawed processes, including the admissibility of evidence extracted under torture or other ill-treatment in making its determinations. The detainee has no access to secret evidence used against him in this process or to legal counsel to assist him. One federal judge found that the CSRT process was unlawful.

If there is no evidence against detainees they should be released. If there is evidence against them then they should be charged and tried, in accordance with internationally accepted standards of fairness, in an independent court that does not impose the death penalty.

Seven law lords began deliberating today whether Britain can use evidence against terror suspects that may have been obtained by torture in other countries.

The case has been brought by eight of the 10 foreign men who were previously detained without charge under anti-terror legislation at Belmarsh high-security prison.

Ben Emmerson QC, for the detainees, told the panel of law lords that the appeal court was wrong to give a ruling last August that permitted the use of evidence that may have been gleaned from torture abroad.

He said the ruling by two of three appeal court judges gave "insufficient weight" to the "constitutional responsibility to suppress the manifestations of torture".

The men making the legal challenge were released after the House of Lords ruled in December 2004 that holding foreign terror suspects indefinitely without trial breached their human rights.

Eight of the 10 Belmarsh detainees are now being held under Home Office control orders that include a form of house arrest. Two of the men have exercised their option to leave the UK.

Mr Emmerson said the case is not about whether information possibly obtained by torture from abroad can be used to stop an attack.

The question under consideration was, he said, whether the evidence can be used in a law court or at a hearing of the Special Immigration Appeals Tribunals (Siac), which holds secret hearings involving terrorist suspects.

The appeal court ruling last August permitted evidence possibly obtained by torture abroad to be used in the detainees' Siac hearings.

Lawyers for the remaining eight men argue that the appeal court ruling breached article 3 of the European Convention on Human Rights, which bans torture or degrading treatment.

The men's lawyers say they are being held on evidence obtained by torture carried out by third parties at the US military detention facility in Guantanamo Bay, Cuba.

"This case raises in acute form the dilemma of any democracy when the judiciary is called upon to reconcile the protection of national security and the protection of human rights," Mr Emmerson told the law lords.

Judgments from the law lords are normally handed down between six and eight weeks after they have heard all of the evidence.

This is the first terrorism-related human rights case to reach the Lords since the July 7 bombings in London, and the first to test whether the judges agree with Tony Blair that believe the suicide bombings have changed the rules of the game".

Lord Carlile, a Liberal Democrat peer appointed by the government to review its anti-terror legislation, has said evidence from possible torture should be used in a way that was "proportional" and not "fixed".

His argument is that the evidence could not be ignored if it indicated dozens or possibly hundreds of lives could be at risk from an attack.

However, Kevin Martin, the president of the Law Society, which will give evidence to the law lords, said the "use of torture is draconian and abhorrent".

"If this ruling is not overturned, we are worried it will prove to be a green light for torturers," he said.

NGOs such as Liberty and Amnesty International argue that the government is chipping away at civil rights, becoming complicit in torture, risking using unreliable evidence and sending a dangerous message to the rest of the world

British victims of torture joined campaigners outside parliament today to sign a petition urging the government to ban evidence obtained by torture abroad.

Bill Sampson, 46, who has dual British and Canadian nationality and lives in Penrith, Cumbria, said that he suffered beatings, sleep deprivation and sexual molestation during 964 days in solitary confinement in Saudi Arabia after being arrested on false charges of terrorism and spying.

"After so many days of that type of brutality, you will say whatever it takes to stop the pain," he said. "From the questions your interrogators are asking you, you can gather what it is that they want to hear and you will tell them it."

Amnesty's UK director, Kate Allen, said: "This is a momentous case. The UK is at an important crossroads. It can reaffirm its stand against torture, which is absolutely banned, or slide towards illegality by its tacit acceptance that torture is sometimes okay."

The hearing was adjourned and will resume tomorrow.