With his governing Conservatives trailing the opposition Labour Party in the polls, Sunak used a speech at a conservative think tank to try to convince voters that only he could defend the country against an "axis of authoritarian states".

He attacked Labour, saying the opposition party could not match his pledge to increase defence spending or tackle illegal immigration and only he had "a clear plan" for the future -- accusations rejected by Labour leader Keir Starmer.

"The next election that our country is going to face is the general election and the choice of that general election is clear -- it's about the future versus the past," Sunak said at the Policy Exchange think tank.

"We have a clear understanding of what the future entails -- the most dangerous time that we have known in a long time but also the most transformational -- and it is only us, it is only me, that has the bold ideas and the clear plan that will deliver a secure future of the country."

Labour responded by accusing the Conservatives of overseeing "costly chaos".

"The only way to stop the chaos, turn the page and start to renew is with a change of government," said Pat McFadden, Labour's national campaign coordinator.

"The Conservatives can't fix the country's problems because they are the problem."

Sunak's pitch to voters sets the scene for what is expected to be an ugly election campaign, with the prime minister's team frustrated at what they believe is a lack of appreciation of what he has achieved in government so far.

Sunak used the speech to go over the policy he has implemented so far, including a pledge to increase defence spending to 2.5% of GDP a year by 2030. But most of the questions to him focused on the difficulties the Conservatives have found themselves in over 14 years in office.

"I am not for one second pretending that everything about the last 14 years was perfect, of course not," he said. "But I am proud of our record."