Two of Britain’s most senior legal figures have ruled for the first time that a secret MI5 policy which allows British security service agents to commit serious crimes is unlawful.

However, the Investigatory Powers Tribunal (IPT) found, by a majority of three to two, that MI5 has the legal power to authorise the commission of criminal offences by agents.

The Northern Ireland-based Pat Finucane Centre (PFC), which was one of four human rights organisations to take the legal challenge against the British government, said the fact that two QCs had dissented was “deeply significant.”

“The overall co-ordination of all security and intelligence matters [in Northern Ireland] lay with MI5 and, as we have seen in the case of [British agent] Brian Nelson and in the murder of Pat Finucane, state agents were involved in murder in this jurisdiction,” a spokesman said. “This is the first time there has ever been dissenting opinions in a judgement from the IPT.”

The PFC and their co-claimants - Reprieve, Privacy International and the Committee on the Administration of Justice (CAJ) - have said they will appeal the tribunal’s decision.

The deputy director of CAJ, Daniel Holder, said the “practice of paramilitary informant involvement in serious crime was a pattern of human rights violations that prolonged and exacerbated the Northern Ireland conflict.

Informant conduct

“Archival documents show that the unlawful nature of informant conduct here was known at the time and it appears policy since has been even more formalised,” he said. “This close ruling is far from the end of the matter.”

In the majority ruling on Friday, the IPT’s president, Lord Justice Singh, its deputy president, Lord Boyd, and Sir Richard McLaughlin said that while the tribunal concluded that MI5 “does have that power as a matter of public law,” it was “important to appreciate that this does not mean that it has any power to confer immunity from liability either under the criminal law or the civil law on either its own officers or on agents handled by them.

“It does not purport to confer any immunity and has no power to do so.”

They also said the “events of recent years, for example in Manchester and London in 2017, serve vividly to underline the need for such intelligence gathering and other activities in order to protect the public from serious terrorist threats.”

Prof Graham Zellick QC, dissenting, said that accepting the British government’s arguments “would open the door to the lawful exercise of other powers of which we have no notice or notion, creating uncertainty and a potential for abuse”.

He said an authorisation to participate in criminality was “in itself intrinsically unlawful: it will impact on the legal rights of others, it may involve the commission of tortious and criminal acts and — in the absence of clear legal authority — is subversive of the rule of law”.

‘Astonished’

It may well be “sensible and desirable, even essential,” he said, “but Parliament would, I fancy, be astonished to be told that it had conferred this power in 1989.”

At a hearing in November, Ben Jaffey QC said the issues raised by the case were “not hypothetical”, submitting that “in the past, authorisation of agent participation in criminality appears to have led to grave breaches of fundamental rights”.

He pointed to the 1989 murder of Belfast solicitor Pat Finucane, an attack later found to have involved collusion with the state, and the case of Freddie Scappaticci, “who is alleged to have been a senior member of the IRA and a security service agent working under the codename ‘Stakeknife’”.

Mr Jaffey told the tribunal at an earlier hearing that “it appears that the Security Service thinks it could, if it thinks it would be in the public interest, authorise participation in murder, torture, sexual assault or other grave criminality in the UK.”

A Home Office spokesman said the “use of covert agents is an essential tool for MI5 as it carries out its job of keeping the country safe.

“We are pleased that the tribunal found in the Government’s favour on all counts and recognised that participating in crime can be a necessary feature of this vital work,” he said.

“We are committed to ensuring that the intelligence and security agencies are supported by government and have the appropriate tools to keep us safe.”