Brown takes starring role at the Festival

The Prime Minister, Gordon Brown, called on ordinary people to "rise up" and do their part in tackling the knife crime that is rampant in some cities when he was quizzed on the subject yesterday by one of Britain's leading crime writers.

Making a surprise appearance to open the 25th Edinburgh Book Festival, Mr Brown was put in the hot seat by the author Ian Rankin, whose gritty Rebus detective stories are best-sellers.

Admitting that knife crime is "our biggest problem at the moment in some cities", the Prime Minister added: "Young people are thinking it is acceptable, fashionable and necessary for them to protect themselves by carrying a knife. But, just like we made guns unacceptable, we should be making knives unacceptable.

"You need role models to do that. You need evidence that carrying a knife makes you less safe, and you need parents and other people saying that knives, like guns, like bullying, like racism, are unacceptable. People in the community have to rise up and say this is unacceptable behaviour. We will see a campaign not just led by government but by people in the country to get knives off our streets, and I think we will see people responding."

Mr Brown spoke about a range of issues, discussing his ideas of "Britishness", fuel prices and education. He studiously ducked questions on his own leadership difficulties, however.

He denied claims by the Conservatives that Britain is a "broken" society. "Britain is still a decent, compassionate society and most people want to see things change for the better," he said.

"A lot of people talk about a broken society. I don't think the British people have ever been broken by anything or anyone."

Giving the example of "a young guy in London they call Britain's young Barack Obama", who helps children from troubled backgrounds, Mr Brown said local heroes could transform violent communities: "Courage is not some godlike quality of fearlessness, but people feeling strongly about things and showing the willpower to do something about it."

Whereas Tony Blair preferred the cosy sofas of daytime TV for informal chats with the public about policy, Mr Brown chose the more cerebral surroundings of a book fair. This, however, laid him open to heckles.

Mr Brown, whose next book will be about "Britishness", spoke about relations between England and Scotland, and fiercely defended the Union. He dismissed the rise of the Scottish Nationalist Party – the largest party in the Scottish Parliament – as a "phase", and said that although the establishment of the Scottish government was right, Scotland's best interests lay with the UK.

"You have got to look at what holds us together," he said. "In 1707, when Scotland joined the Union with England, only 3 per cent of Scots had English relatives and most had nothing to do with people in England. Today 50 per cent of Scots have relatives in England, so it does sound strange that people are talking about us splitting up when there is such a level of connection.

"We share the same bonds of our liberty, democracy, social cohesion and respect for the same institutions. I wouldn't like a Scot to be denied healthcare in England, and there are economic connections and big questions of environment and security... On an island, all of us are together. A partnership on equal terms is the right thing for the future."

Mr Brown added that oil prices and food shortages needed global action. "The problems we have can only be sorted globally," he said. "If we don't play our part in helping Africa and other countries to solve their problems, other people will offer easy solutions, including the route to terrorism. This is a security problem, as well as a moral, ethical and social problem."

He identified solving Africa's food production problems, raising standards of education and fighting disease worldwide as priorities for a UN summit next month. "What we have to build up, and this is the lesson of Barack Obama and everybody else, is this idea of global citizenship: that we have responsibilities to each other and share the same ideas as each other."

Asked what his one wish would be before he finished in politics, he said: "I want [Burma's democratically elected leader] Aung San Suu Kyi not only to be released but to be in power in Burma."