Kincora boys' home abuse: Files handed to HIA inquiry
The discovery of new state papers about the Kincora abuse scandal does not mean the inquiry into what happened should be extended, the NI secretary has said.
There is pressure to include the east Belfast boys' home in the Goddard abuse inquiry in England and Wales.
However, Theresa Villiers said the right place for the new files to go was the Northern Ireland Historical Institutional Abuse Inquiry (HIA).
It cannot compel witnesses or documents from agencies like MI5.
New government files containing allegations about Kincora have been handed over to the HIA.
Three senior care staff at Kincora were jailed in 1981 for abusing 11 boys. At least 29 boys were abused at the home between the late 1950s and the early 1980s.
Ms Villiers said the inquiry, chaired by Sir Anthony Hart, was "doing an exceptionally good job".
"We feel that that is the best forum to investigate these despicable events which took place at Kincora," she said.
"Like everyone else we want to ensure that the truth is discovered, that these events are fully investigated and we believe that the Hart inquiry is the best forum to do that."
The papers should have been disclosed as part of a previous search of Home Office documents.
However, they were not discovered as they were not properly catalogued.
While the details of the files have not been made public, it is known they include Kincora abuse claims passed to the authorities by ex-Army press officer Colin Wallace.
It is understood that the Kincora scandal is also mentioned in a file about the late former Northern Ireland minister and Conservative MP Sir William van Straubanzee, who died in 1999. That document was meant to have been destroyed in 2013.
An official review into whether there was a Westminster cover-up of paedophile activity in the 1980s concluded last November, but these files were not found.
Accompanying the files is a letter from the Permanent Secretary of the Cabinet Office Richard Heaton in which he apologises for the errors.
"I can also confirm that relevant papers have been drawn to the attention of the Historic Institutional Abuse Inquiry led by Sir Anthony Hart," Mr Heaton writes in the letter.
"Sir Anthony has already started to review these."
Other documents not related to Kincora but thought to be relevant to the Goddard inquiry into abuse in England and Wales have also been discovered.
Among those files are government papers and correspondence about the former Home Secretary Leon Brittan, Mrs Thatcher's former parliamentary secretary Sir Peter Morrison and the former diplomat Sir Peter Hayman. All three of those men are now dead.
Analysis: Chris Buckler, BBC Ireland correspondent
The claims of a cover-up about who was involved in abusing boys at Kincora will be fuelled by the discovery of these documents.
However, at this stage we do not know if they provide any new light on what took place in the east Belfast boys home.
The Cabinet Office insists the files were not hidden - they say they simply were not originally found.
But that is deeply embarrassing, given the spotlight and scrutiny on Westminster about allegations of abuse involving people in positions of power.
What the documents do prove is that questions about Kincora were raised and discussed by government officials right through the 1980s and 1990s.
While the Home Secretary has so far refused to include Kincora in the Westminster-based Goddard inquiry, there will be mounting pressure to extend that scope.
Campaigners will argue that it is difficult to separate London and Belfast when these papers provide a trail that leads between them.
Amnesty International's Patrick Corrigan said: "The (HIA) inquiry headed by Sir Anthony Hart simply does not have the power to compel the production of documents such as these or indeed witnesses from central government to come forward and lay bare what happened at Kincora.
"The Westminster inquiry does have those powers - it is absurd that the government continues to exclude Kincora from that inquiry that actually does have the powers to finally reveal the truth."