Lawyers for Mr Flynn, a survivor of two failed UVF attacks, said they have already established an admission from the PSNI that its predecessor, the RUC, misused its powers in handling paramilitary agents.

The PSNI has agreed to pay Mr Flynn damages for the negligent acts of the RUC, as the inheritor of its legacy.

However, police officials have refused to provide material which Mr Flynn’s lawyers say could determine the extent of the wrongdoing and contribute to the amount of damages.

The PSNI said providing the material would have disproportionate implications for costs and resources.

In his judgment, Mr Justice Adrian Colton, sitting in the High Court, ruled: “The defendant says that it would be disproportionate and unduly oppressive for the court to make an order requiring him to disclose the documentation sought in this application, in light of the admissions which have been made … Whilst I do accept that an order for specific discovery in this action may well be laborious and time consuming I consider that there is a force in the plaintiff’s submission that the defendant has not taken its discovery obligations seriously at least prior to the admission defence.

“The statement of claim in this action was served on 14th November 2011. Despite a number of court orders and the freestanding obligation to provide discovery irrespective of any application brought on behalf of the plaintiff it appears that no steps were taken by the defendant to prepare a list of documents in this action.”

In conclusion, he said the material provided by the PSNI did not comply with the appropriate rules of the court.

Solicitor Claire McKeegan at Belfast firm KRW Law, who is instructed by Mr Flynn, said: “We are very pleased with the decision of Mr Justice Colton. The PSNI have tried at every turn to avoid disclosing any relevant material to allow us to resolve this case. In light of today’s decision we will be engaging with the legal representatives of the PSNI to ensure that full disclosure is made urgently.

“This decision is important not only to the matter at hand but to all of our Legacy litigation where the state representatives have cited resources as justification for non-compliance with the rules. We see today’s decision as a marker that this position will not be accepted.”