The government has said it is "truly sorry" for the events at Ballymurphy 50 years ago in which 10 innocent people were killed.
Northern Ireland Secretary Brandon Lewis made the apology in the Commons.
It comes after a coroner on Tuesday concluded the victims of shootings over three days in August 1971 were "entirely innocent" and the British Army was responsible for nine of the fatal shootings.
Mrs Justice Keegan found that the use of lethal force by soldiers was not justified.
She also criticised the lack of investigation into the 10th death, that of John McKerr, and said she could not definitively rule who had shot him.
Downing Street said Boris Johnson "apologised unreservedly on behalf of the UK government for the events that took place in Ballymurphy" during a phone call with Northern Ireland First Minister Arlene Foster and deputy first minister Michelle O’Neill on Wednesday.
But the prime minister was accused of "bad manners" and of neglecting to be "serious" in his response.