Former prime minister gives verdict on unrest and says that politicians are 'missing the point' talking about a broken society

Tony Blair has launched a fierce attack on widespread claims that this summer's riots showed that British society is in "moral decline". The former prime minister warns that rash talk of a broken society threatens to harm the country's reputation abroad.

While admitting that he was guilty of a similar reaction to the murder of two- year-old Jamie Bulger in 1993, he calls for the government not to play politics with the crisis and mounts an impassioned defence of Labour's legacy after 13 years in power.

Writing in the Observer, in his first public verdict on the riots, Blair says: "In 1993, following the Bulger case, I made a case in very similar terms to the one being heard today about moral breakdown in Britain. I now believe that speech was good politics but bad policy. Focus on the specific problem and we can begin on a proper solution.

"Elevate this into a highfalutin wail about a Britain that has lost its way morally and we will depress ourselves unnecessarily, trash our own reputation abroad, and worst of all, miss the chance to deal with the problem in the only way that will work."

During a speech on Monday, David Cameron said that he was determined to tackle a "slow-motion moral collapse" in Britain and mend the country's "broken society". He attacked the influence of human rights legislation and claimed that some of the worst aspects of human nature had been "tolerated, indulged – sometimes even incentivised – by a state and its agencies that in parts have become literally demoralised".

But in a rare intervention into British politics since he left Downing Street, Blair defends the society Labour helped to build and says he believes this generation is more respectable, responsible and hard-working than his own.

While commending parts of both Cameron's and Labour leader Ed Miliband's speeches, in a thinly veiled attack on the prime minister, he adds: "I think we are in danger of the wrong analysis leading to the wrong diagnosis, leading to the wrong prescription".

Amid tensions between Downing Street and Scotland Yard over the early handling of the riots, Blair also calls for the government to support the police. "The police need to know they have strong support," he writes. "They need to feel it from politicians and public alike."

He also rails against the "muddled thinking" of those on both the left and the right who, he claims, "miss the point" about the cause of the riots two weeks ago.

Blair, who was prime minister from 1997 to 2007, says that neither social deprivation nor a lack of personal responsibility is at the root of the problem. Instead, he says, Britain, like "virtually all" developed nations, needs to deal with a group of people who are beyond the pale.

"The big cause is the group of alienated, disaffected youth who are outside the social mainstream and who live in a culture at odds with any canons of proper behaviour. And here's where I simply don't agree with much of the commentary. In my experience they are an absolutely specific problem that requires a deeply specific solution.

"The left says they're victims of social deprivation, the right says they need to take personal responsibility for their actions; both just miss the point. A conventional social programme won't help them; neither – on its own – will tougher penalties.

"The key is to understand that they aren't symptomatic of society at large. Failure to get this leads to a completely muddle-headed analysis of what has gone wrong. Britain as a whole is not in the grip of some general 'moral decline'."

He adds: "This is a hard thing to say, and I am of course aware that this too is generalisation. But the truth is that many of these people are from families that are profoundly dysfunctional, operating on completely different terms from the rest of society, either middle class or poor.

"This is a phenomenon of the late 20th century. You find it in virtually every developed nation. Breaking it down isn't about general policy or traditional programmes of investment or treatment."

Blair writes that at the end of his time in government he realised that the solution was intervention family by family, a reform of criminal justice around antisocial behaviour, organised crime, persistent offenders and gangs.

But in a dig directed towards Gordon Brown, his successor in 10 Downing Street, he adds: "The agenda that came out of this was conceived in my last years of office, but it had to be attempted against a constant backdrop of opposition, left and right, on civil liberty grounds and on the basis we were 'stigmatising' young people.

"After I'd left, the agenda lost momentum. But the papers and the work are all there."