The government is pushing a justice and security bill that allows sensitive intelligence to be presented to a judge by officials while preventing victims and claimants from knowing the allegations against them in full.
Officials say the move is designed to protect national security by preventing confidential information from being exposed.
Amnesty said in a report published on Monday that the secret courts plan gives the government the power to "simply play the 'national security' card whenever it wants to keep things secret".
"[It poses] a real threat to the principles of fairness and open justice in the UK - principles which should always be at the heart of the justice system,” Amnesty’s UK researcher Alice Wyss said.
The report-- called Left in the Dark: the use of secret evidence in the UK-- says the new bill will substantially extend the use of the so-called closed material procedures (CMPs) even to the cases where the government faces a lawsuit for human rights violations such as torture and enforced disappearance.
Amnesty said the government can already rely on secret evidence in at least 21 different contexts.
The report quoted a 43-year-old man who had been sentenced to detention and living under highly restrictive conditions for ten years based on evidence he has never seen.
“Evidence that is kept secret, lawyers that can’t talk to you - it’s a secret justice system straight from the pages of a Kafka novel,” Wyss said.
“The Justice and Security Bill will enable the government to throw a cloak of secrecy over wrongdoing. We want the House of Lords to reject this bill unless it is very seriously amended, with the secret justice components removed,” she added.