The UK Government has apologised for "any failings by the police" in trying to bring the "terrorists" behind the Loughinisland massacre to justice.
But Northern Ireland Minister Kris Hopkins shied away from calls for a British Government apology to the victims, survivors and their families following the 1994 murders in which six Catholic men were shot dead by the Ulster Volunteer Force (UVF).
Theresa May was later also pressed by the SDLP's Margaret Ritchie (South Down) to ensure prosecutions are pursued, an apology is forthcoming and compensation provided.
The Prime Minister described the Loughinisland killings as a "terrible evil" and said it was for the Police Service of Northern Ireland (PSNI) to pursue the case.
Six people were killed and five injured when two UVF gunmen burst into a packed bar at around 10.10pm on June 18 1994 and fired at customers watching the Republic of Ireland play Italy in the World Cup in the US.
Significant police collusion with the murderers was exposed by a damning investigation by Northern Ireland's Police Ombudsman Michael Maguire.
No-one has ever been brought to justice.
Mr Hopkins, replying to a parliamentary debate in Westminster Hall, reaffirmed that the UK Government accepts the police ombudsman's report.
He noted PSNI Chief Constable George Hamilton has twice apologised to the families and accepted officers involved in collusion should be held to account.
Mr Hopkins added: "We have judged our security forces against the highest standards of integrity and professionalism in the past, and we always will.
"As a government, we have been more forthcoming than any of our predecessors in accepting where the state has failed to live up to the highest standards and in apologising when it is the right thing to do. Where it is warranted, we will continue to do so.
"There have been calls for the UK Government to apologise for what happened on the fateful day of 18 June 1994.
"Of course the Government deeply regrets that the terrorists who committed these vicious attacks have never been brought to justice, and we are sorry for any failings by the police in relation to this case.
"However, the Ombudsman's report makes it very clear that those responsible for this despicable attack were the Ulster Volunteer Force terrorist gang who planned it and carried it out, leaving utter devastation in the aftermath and for many years thereafter.
"The report also categorically states that the police had no prior knowledge of the attack that would have enabled them to prevent it.
"The Government will never seek to defend the security forces by defending the indefensible."
Ms Ritchie earlier said she wanted a "more helpful" response from the British Government after former Northern Ireland Secretary Theresa Villiers "insulted" the people of Loughinisland, the families and victims.
Ms Villiers referenced Loughinisland in a speech earlier this year about what she claimed was a "pernicious counter-narrative" of the Troubles that was trying to place undue blame on the security forces.
Speaking during the debate, Ms Ritchie said: "There must now be accelerated work on prosecutions, a British Government apology to the victims and survivors and their families, and provision of compensation for the victims, for those lost lives."
Those murdered were Barney Green, 87, Adrian Rogan, 34, Malcolm Jenkinson, 53, Daniel McCreanor, 59, Patrick O'Hare, 35, and Eamon Byrne, 39.