Tony Blair has called for the international community to present a united front against North Korea’s nuclear programme but predicted difficulties in successfully disarming the Pyongyang regime.

Speaking by satellite link to a conference in Tokyo, Mr Blair said that, unlike Libya, which gave up its nuclear programme voluntarily in 2003, North Korea showed no interest in rejoining the international community for the wellbeing of its people.

“One of the tragedies of North Korea is the state of its economy and its people and the misery that they live under,” Mr Blair said from Downing Street to a conference organised by The Times and the Yomiuri newspaper in Japan. “I’m afraid . . . that it’s only when such a regime is prepared to embrace the modern world in a full way that they’ve got the motivation to make the changes in terms of its stance on weapons of mass destruction. So I think it’s going to be very tough with North Korea.”

Britain supported the UN Security Council resolution imposing mandatory sanctions on North Korea after it tested a nuclear weapon in a remote mountain bunker last month, but its denunciations of Pyongyang have been less prominent than those of the US, Japan — which has joined the US and South Korea in agreeing not to recognise North Korea as a nuclear weapons state — and even China.

Last month John Prescott, the Deputy Prime Minister, avoided any public comment during a tour of Japan, Korea, China and Malaysia.

Yesterday the Prime Minister stopped short of calling for the overthrow of Kim Jong Il, the North Korean leader. “The plight [of North Korea’s] people will appal anyone,” he told the audience of businessmen, academics, journalists and diplomats from Japan, Europe and the US. “Its people are living in poverty while the Government pursues its nuclear ambitions. I hope in time we come to see a different situation there.”

North Korea agreed last week to attend another round of talks with South Korea, China, Japan, Russia and the US, which are being held in Beijing. “The six-party talks succeed if the main countries engaged in them stick together and deliver a strong and firm message,” said Mr Blair.

“The one thing I think you can be sure of in a situation like this is that the only language that will be understood by the North Korean regime is one of firmness . . . the firmer we are, the more likely we are to succeed.”

He also praised Shinzo Abe, the Japanese Prime Minister, who also spoke at the conference, for his promise to take Japan in a more self-assertive direction. “What is immensely exciting, as I watch Japan from afar, is the way that Japan today is changing, slowly but surely, its place in the world,” he said. “I want to see that process continue further. It’s good for Japan and for the region and for the wider world.”

Mr Abe has alarmed liberals with his promises to revise Japan’s “peace” constitution, which currently restricts the country’s armed forces to a strictly defensive role.

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