The slump in Gordon Brown’s fortunes over the past year has been mirrored by the rise in David Cameron’s stock. The Conservative leader, who last summer was accused of underestimating the prime minister, is now revelling in his opponent’s discomfort. Big opinion poll leads can evaporate overnight, as Mr Brown discovered last autumn. But the lead for Mr Cameron, 22 points in today’s YouGov poll for this newspaper, is important because it allows him to develop policy at his own pace. Although it is still unclear what a Cameron-led government would be like, the veil is gradually being lifted.

Last week, campaigning in the Glasgow East constituency where even a resurgent Tory party has a zero chance of winning, Mr Cameron made what could be one of his more important speeches. In a part of the nation that has better claims than most to be a symbol of Britain’s broken society, he set out some ideas for fixing it.

The Tories, thanks to their former leader Iain Duncan Smith, have something to say on this. His Centre for Social Justice did its work in Glasgow East among the fractured families, drug addicts and alcoholics. The two reports he produced for the Conservatives’ Social Justice Policy Group, Breakdown Britain and Breakthrough Britain, analysed the problem in precise detail. The work he has been pioneering with charities, community groups and social entrepreneurs is making a difference.

The question is whether efforts like these can do more than arrest society’s decline. Nor does the solution lie with top-down efforts such as Labour’s New Deal which, as the OECD pointed out last week, has failed young people and left us with a generation of “neets” (not in education, employment or training). Mr Cameron has some good initial ideas for education, health and welfare reform and advocates a much tougher approach to knife crime.

The reason why his speech was important, however, was because of what he said about personal responsibility. He argued that we live in a culture in which the default position is to blame somebody else. People are the “victims” of obesity, rather than slobs who stuff themselves with food. They are “at risk” of poverty, social exclusion, drug addiction or alcoholism. As he put it: “It’s as if these things . . . are purely external events like a plague or bad weather.”

Some of this, of course, is a result of government policies. If you create a nanny state, you should not be surprised if people behave like children. Big government is the enemy of personal responsibility. Part of it reflects changes in political attitudes. John Major once said we should condemn more and understand less; his influence was such that politicians have done the opposite. Mr Cameron appeared to be guilty of this with his “hug a hoodie” speech. What he said last week was not inconsistent with tackling the underlying causes of crime, antisocial behaviour and family breakdown but it did signal an important change of tone.

“We as a society have been far too sensitive,” he said. “In order to avoid injury to people’s feelings, in order to avoid appearing judgmental, we have failed to say what needs to be said. We have seen a decades-long erosion of responsibility, of social virtue, of self-discipline, respect for others, deferring gratification instead of instant gratification. Instead we prefer moral neutrality, a refusal to make judgments about what is good and bad behaviour, right and wrong behaviour. Bad. Good. Right. Wrong. These are words that our political system and our public sector scarcely dare use any more.”

There are Thatcherite echoes here for moral conservatives, but even those of liberal inclination will think that society would be better if people took more personal responsibility. One of the most pressing tasks for any future government will be to put society back together at a time when the economic legacy may be grim. This requires, first and foremost, that people take responsibility for their own actions. Mr Cameron is to be applauded for saying so. Now he needs to follow through.