On Tuesday, part II of the Justice and Security Act – popularly known as the Secret Courts Act – came into force. The act gives a green light to UK courts to hear national security claims in secret – excluding claimants, their lawyers and the press – and to give judgment after hearing an unchallenged case presented by one side, usually the government.

Speculation about the cases which the government has lined up for consideration under "closed material procedures" is rife. These procedures are unnecessary, unprincipled and unfair. They amount to the wholesale removal of the ability of the courts and the public to effectively scrutinise any claim where any risk to national security is raised; no matter how slight that risk or how serious the wrongdoing alleged.

Unfortunately, draft rules of court hastily thrown together at the Ministry of Justice would set aside the overriding objective of our courts to do justice in favour of absolute secrecy in any case where national security is raised by ministers. Extremist threats have, throughout history, threatened our shared democratic values. This is no different today. However, measures such as those included in this act subvert centuries of common law cultivated to protect our standards of open, equal and adversarial justice. Last week, our supreme court urged caution in the first case where the justices were reluctantly persuaded to sit in secret. Their judgment expressed some regret that the government may be too quick to overstate the need for secrecy. In the words of Lord Hope – one of four who would have resisted the use of these "obnoxious" procedures – secret justice of this kind is "really not justice at all".

Shami Chakrabarti Director, Liberty

Andrea Coomber Director, Justice

Kat Craig Legal director, Reprieve

Cori Crider Strategic director, Reprieve

Simon Crowther

Rosa Curling Leigh Day

Professor Helen Fenwick Durham University

Allan Hogarth Head of policy and government affairs, Amnesty International

Professor Fiona de Londras Durham University

Sam McIntosh City University London

Nicholas Mercer

Eric Metcalfe Monkton Chambers

Rowena Moffatt Lamb Building Chambers

Joanna Shaw

Richard Stein Leigh Day

Katy Vaughan Swansea University

Prof Adrian Zuckerman Oxford University