Some information from the Troubles can never enter the public domain because it would put lives at risk, the Northern Ireland Secretary has said.
National security is the primary responsibility of the Westminster Government, James Brokenshire added.
Sinn Fein accused him of hiding behind security issues and blocking the release of money for inquests into conflict killings.
Mr Brokenshire said: “National security remains the primary responsibility of the UK Government and (in) our actions we will certainly continue to have that at the forefront of our minds.”
Sinn Fein and the British Government have been at loggerheads over the issue.
The dispute has hindered efforts to reach a deal on tackling the legacy of past violence and the release of money for inquests into Troubles deaths.
DUP leader Arlene Foster blocked a bid to request the extra money from the Government amid fears of an imbalance between the number of inquiries into state killings and those involving paramilitaries.
Victims held a protest at the delay at Stormont on Wednesday.
One group represents 10 people killed by soldiers in Ballymurphy in west Belfast in 1971 as the then government introduced internment - imprisonment without trial.
They urged politicians engaged in powersharing talks at Stormont not to enter government until there is agreement on addressing the legacy of the past.
Sinn Fein leader at Stormont Michelle O’Neill said: “James Brokenshire and the British Government need to stop hiding behind the issue of national security.
“These families have the right to an inquest. It should not be subject to a political veto.
“The British Government needs to stop being a blocking mechanism. They need to deliver for these families.”
Former Northern Ireland secretary Theresa Villiers raised the issue with Mr Brokenshire in Parliament.
She said: “The Government and the police have disclosed unprecedented amounts of information about the Troubles, some of it extremely sensitive.
“But will the Secretary of State agree that there is some information that is so sensitive that it can never go out into the public domain, because it would put lives at risk if it did?”
Mr Brokenshire replied: “I do agree with her, and with all of her experience as a previous secretary of state she knows the sensitivity and importance of these issues of national security.”
He said devolved government can return to Northern Ireland, and praised a “shared willingness” among the parties to re-establish the ministerial Executive after the collapse of powersharing at Stormont.
He added that “significant challenges” remained but progress had been made and needed to continu urgently to reach a positive outcome.