The Prime Minister has pledged to fight the "increasing" threat from dissident republicans.
Speaking at his party's conference in Birmingham, David Cameron said he would use "every means at our disposal" to combat the threat.
He also paid tribute to his predecessors for their contribution to the peace process and said he would continue their work.
He added that he was right to apologise for Bloody Sunday.
"When this country has got it wrong, we'll admit it, as I did when I apologised for Bloody Sunday," Mr Cameron told delegates.
He spoke about Northern Ireland when pledging to be a prime minister for all of the United Kingdom.
"Tony Blair, Gordon Brown - and John Major before them - worked hard to bring lasting peace to Northern Ireland and I will continue their work.
"And as the threat of dissident republican terrorism increases, I want to make it clear that we will protect the people of our country with every means at our disposal.
"When I say I am prime minister of the United Kingdom, I really mean it.
"England, Scotland, Wales, Northern Ireland - we're weaker apart, stronger together, so together is the way we must always stay."
Earlier, the secretary of state told the conference that dissident republicans would not be allowed to "drag Northern Ireland back to a bloody past".
Owen Paterson said the government did not underestimate the dissident threat.
"We'll do everything in our power to pursue these criminals, to disrupt them and prevent them from achieving their aims," he said.
"Co-operation between this government, the local justice minister, the PSNI and our partners in the Republic of Ireland is unprecedented."
He said the government would never compromise on security.
Dissident republicans have carried out several attacks in Northern Ireland this year, the most recent a car bombing in Londonderry on Monday night.
Speaking about the economy, Mr Paterson said Northern Ireland was far too dependent on its public sector, saying public spending accounted for "a staggering" 77.6% of GDP.
He said this was unsustainable and the private sector had to be expanded.
"That's why, along with the Treasury and Stormont ministers, we're working on a long term-plan to re-balance the economy," he said.
"We're examining proposals to turn Northern Ireland into an enterprise zone.
"And, as we promised at the election, we'll look at potential mechanisms for changing the corporation tax rate in Northern Ireland to attract major new investment."
Mr Paterson warned it could take 25 years to rebalance the NI economy.
He also pledged to help Presbyterian Mutual Society savers who lost money when the PMS crashed in November 2008.
"Last year, referring to the banking crisis, Gordon Brown boasted that 'not one British saver has lost a single penny'," he said.
"In saying this he completely ignored those investors in the Presbyterian Mutual Society who saw their money disappear."
Mr Paterson added that new talent had to be encouraged in Northern Ireland politics.
"So we'll end 'double jobbing' at Stormont and Westminster by consent if possible, by law if necessary."
The secretary of state also reiterated that there would be "no more costly and open-ended public inquiries".
He hit out at those in Northern Ireland who wanted to "re-write history".
"They want to put our brave police and soldiers on an equal footing with those who sought to destroy democracy," he said.
"Let me be clear - we will never be party to that."
However, he added the government would acknowledge when the state, or those who served it, had failed "to uphold the highest standards" as in the case of Bloody Sunday.
Prime Minister David Cameron is also expected to strongly criticise the activities of dissident republicans in his speech to the conference later.
His first speech to the party faithful as prime minister is thought to include several Northern Ireland references.
He is expected to say he is prime minister for all parts of the UK.
It is believed he will pledge continued support for the peace process, pointing out how Tory governments were involved at the outset of talks in the 1990s.