Controversial Government proposals to ban prosecutions for Troubles murders should be considered “on their merits, however painful it is”, former Northern Ireland secretary Lord Mandelson has told Parliament.

Given the remote possibility of cases being brought to trial, the Labour peer argued that those who carried out crimes were effectively “being shielded by the rule of law, not living in fear of it”.

As such it was “reasonable to weigh alternative approaches”, he said.

The likelihood of prosecution is remote

He made his comments in response to the contentious plan to introduce a statute of limitations on crimes committed during the Northern Ireland conflict up to April 1998 and would apply to military veterans as well as ex-paramilitaries.

The proposals, which Prime Minister Mr Johnson said would allow Northern Ireland to “draw a line under the Troubles”, would also end all legacy inquests and civil actions related to the bloody period.

In addition, the package of measures included a new truth recovery body and an oral history initiative.

However, the move has been heavily criticised by all the main political parties in Northern Ireland as well as the Irish Government, and a range of victims’ and survivors’ groups.

Speaking at Westminster, Lord Mandelson said: “It must be right in principle that every family bereaved in the conflict should have access to an effective investigation and meaningful process of justice, regardless of the perpetrator.

“This, rightly, has guided every Government since the Good Friday agreement. However, in practice, we must be honest with ourselves that effective, conclusive investigations in the numbers demanded is simply not possible.

“The likelihood of prosecution is remote and therefore the original perpetrators, for all practical purposes, are being shielded by the rule of law, not living in fear of it.

“Therefore, it is reasonable to weigh alternative approaches.

“We should consider the Government’s proposals on their merits, however painful it is – and I acknowledge that it is painful – for victims’ families to accept a statute of limitations.”

He added: “However, there is a suspicion that the Government might be half-hearted about a system of information retrieval if it is introduced, and that the Prime Minister let the cat out of the bag when he talked of drawing a line under the so-called Troubles the other day.

“Does the minister accept that if any new body is created to retrieve information and confront people with the truth, it must be genuinely independent and powerful – fearless and fearlessly led? If not, it would be much worse than useless. It would be an insult to, and a betrayal of, every bereaved family in Northern Ireland.”

Responding, Tory frontbencher Viscount Younger of Leckie said: “I reassure him that we indeed wish to set up a fully independent body to look at this.”

He added: “Northern Ireland has already seen difficult but necessary measures put in place that have in the past put aside normal criminal justice processes for the cause of peace and reconciliation.

“He will know that this includes the early release of prisoners, restricting prison sentences to just two years, even for the most heinous Troubles offences, and concluding the process of secretly decommissioning paramilitary weapons.

“Therefore I believe he is right that we are in a position where we need once again to explore alternative proposals.”