British security forces colluded with paramilitary killers during the Troubles in Northern Ireland, resulting in the still unsolved murders of hundreds of people, the BBC investigative series Panorama has revealed.

Now, Amnesty International is calling for a full-fledged investigation into the claims.

The program, “Britain’s Secret Terror Deals,” which aired Thursday on the BBC, zeroed in on links between MI5, the British Army and the Royal Ulster Constabulary with the Ulster Defense Association and the Ulster Volunteer Force. It also explored allegations made by the the families of victims killed by the IRA that some of those who perpetrated the killings were also paid informers for the British state.

Northern Ireland’s first police ombudsman, Baroness Nuala O’Loan, was among those interviewed by reporter Darragh McIntyre and the Panorama team.

She described some of the people working as undercover operatives for the British forces as “serial killers.”

"They were running informants and their argument was that they were saving lives, but hundreds and hundreds of people died because these people were not brought to justice.

"There was impunity really for these people to go on committing their crimes. Many of them were killers, some were serial killers," she said.

According to Lord Stevens, the former Met Police Commissioner who has headed three government investigations into Troubles-era security forces in Northern Ireland, thousands of agents and informants were recruited.

The current police ombudsman of Northern Ireland, Dr. Michael Maguire, has been for a number of year now investigating 60 murders in which the state has been implicated.

It was not until last year, when he challenged the Police Service of Northern Ireland (PSNI) in court, that the PSNI agreed to release the relevant files.

Speaking to Panorama, PSNI Chief Constable George Hamilton said “There is a need to understand the sheer magnitude of what we are dealing with. We are talking about rooms full of material.

"Some of it is very sensitive, some of which if it is released in the wrong circumstances would be outside of legislation, some of it if released in the wrong circumstances could put lives at risk."

Amnesty International has been firm in its calls for a full investigation. "The breadth and depth of collusion being alleged here is truly disturbing,” said Amnesty Northern Ireland Program Director Patrick Corrigan.

"Killing people targeted by the state, using intelligence provided by the state and shooting them with guns provided by the state - if all this is proven, we’re not talking about a security policy we’re talking about a murder policy.

"There must now be a full, independent investigation into the scale of the policy where the police, army and MI5 worked with illegal paramilitary groups, resulting in the deaths of perhaps hundreds of people.

"Without full accountability for past actions, there can be no public confidence in today’s justice mechanisms."

To date, the British government’s response to these claims has been that collusion with paramilitaries should not have been carried out and that it has already apologized in the instances in which it was practiced.