UK security services helped devise act that gave amnesty over Troubles killings

Revelation that policing and state agency figures were in secret policymaking group angers victims' groups

The British security services were involved in formulating the controversial Legacy Act, which offered an amnesty to soldiers and paramilitiaries despite MI5's role in many killings during the Northern Ireland Troubles, it can be revealed.

The presence of policing and state agency figures among a secret policymaking group involved in devising the act - a fact established through an investigation by Belfast-based newsletter the Detail and shared with the Guardian - has angered victims' groups already critical of the legislation.