The Sinn Féin leader said she has a sense of “sorrow and regret” for everyone who was hurt and harmed during the conflict in Northern Ireland.
Mary Lou McDonald said that a report into the operation of the British Army’s top agent inside the IRA was “comprehensive and deeply shocking”.
She made the comments following the publication of the interim findings of Operation Kenova, which examined 101 murders and abductions linked to the Provisional IRA’s so-called “nutting squad”.
The IRA’s internal security unit (ISU) was responsible for interrogating, torturing and murdering people suspected of passing information to the security forces during the conflict.
The report calls on the republican leadership to apologise to bereaved relatives and victims of the ISU and those who suffered under linked campaigns of intimidation against them.
Speaking at Dublin Castle, Ms McDonald said: “The report is comprehensive and it is deeply shocking and I’m conscious of families that have suffered grievous wrong.
“I hope that this report brings a sense of vindication for them because they’ve told their stories of the… not just the pain of their loss, but the kind of the stigma that they lived with for a very, very long time.
“The report asked for a number of things, including acknowledgement on the part of republicans, and you’ll have heard my colleague Michelle O’Neill speak yesterday.
“I want to reiterate that sense of sorrow and regret for everybody who was who hurt and harmed, without exception.
“The story tells itself. It’s a case of a very shadowy, very murky affair, where the British state had a hand in running agents and lives were lost as a consequence, and that is a deplorable situation.”
Asked if she accepts that the IRA killed members of its own community, Ms McDonald said: “It was as the report has told, and a very, very dark period in history.
“I can only say that is history, and our job now is to build towards a better future and I am absolutely determined, as you well know, to be part of that.”