This week's attempted terrorist attack demonstrates "how severe the terrorist threat continues to be" in Northern Ireland, Theresa Villiers has said.
The Northern Ireland Secretary praised the "highly effective action" of the Police Service of Northern Ireland (PSNI) and its partners in averting mass casualties, adding the Government remained vigilant on this threat.
Four mortar bombs were seized in Londonderry on Sunday night.
Her comments came as David Rutley, Conservative MP for Macclesfield, asked during Northern Ireland questions in the Commons: "In light of the recent successful interception of four mortar bombs by the police in Northern Ireland, can she tell the House what steps she's taking to counter the work of terrorists whose aim is to maim and kill innocent people?"
Ms Villiers replied: "The attempted terrorist attack this week demonstrates how severe the terrorist threat continues to be in Northern Ireland. It was only through the highly-effective action of the PSNI and its partners that mass casualties were averted, the Government remains vigilant on this threat and has included it as a tier one priority in its national security strategy."
She added she had regular discussions with the First and Deputy First Minister and other political leaders in Northern Ireland about the disturbances of recent months and a way forward could only be found through dialogue and working together.
DUP parliamentary group leader Nigel Dodds said: "The interception of the mortar bomb attack obviously saved a devastating attack on Londonderry and saved lives. Can she tell us in light of the string of attacks and attempted attacks from that particular quarter what extra resources she is willing to give in the coming year to Northern Ireland and the police and security forces to counter the dissident threat?"
Ms Villiers replied that, shortly after taking office, the coalition devoted an extra £200 million to national security priorities in Northern Ireland which had been "tremendously helpful" to the PSNI.
She added discussions would continue on the issue of successive funding when that £200 million runs out and the Government would continue to "do everything we can to support the PSNI and its partners and the Northern Ireland Executive in countering this threat".
Shadow Northern Ireland Secretary Vernon Coaker also paid tribute to the "bravery and success" of the police in preventing a terrorist attack in Londonderry on Sunday night. He said: "Those who seek to destroy the peace and progress will not succeed, but we have to remain vigilant to the threat that they pose."