LONDON — The conservative leader David Cameron attacked the culture of “moral neutrality” yesterday, calling on the obese, the idle, and even the poor to accept some responsibility for their plight.

The Opposition leader said Britain risked creating a society where nobody was prepared to tell the truth “about what is good and bad, right and wrong.”

Society had become “far too sensitive” to people’s feelings, with no one prepared to say “what needs to be said.”

Speaking during a visit to a deprived area of Glasgow, Mr. Cameron added: “Instead we prefer moral neutrality, a refusal to make judgments about what is good and bad behavior, right and wrong behavior.

“Bad. Good. Right. Wrong. These are words that our political system and our public sector scarcely dare use any more.”

“We talk about people being ‘at risk of obesity’ instead of people who eat too much and take too little exercise.

“We talk about people being at risk of poverty, or social exclusion — it’s as if these things, obesity, alcohol abuse, drug addiction — are purely external events like a plague or bad weather.”

Mr. Cameron said he accepted that personal circumstances — such as where someone was born, their neighborhood, their school, or their parents — had a “huge impact” on their lives.

But on a day when a 14-year-old boy became the 19th teenager to die from stab wounds in London this year, he insisted social problems were often the consequence of people’s own choices.

The erosion over several decades of “responsibility, of social virtue, of self-discipline” and “respect for others” had led to a culture of “instant gratification” and a lack of boundaries on people’s behavior, Mr. Cameron said.

“Social problems are often the consequence of the choices people make.

“There is a danger of becoming quite literally a de-moralized society, where nobody will tell the truth any more about what is good and bad, right and wrong.

“That is why children are growing up without boundaries, thinking they can do as they please, and why no adult will intervene to stop them — including, often, their parents. If we are going to get anywhere near solving some of these problems, that has to stop.”

The Tory leader acknowledged that he risked attracting attention to his party’s behavior, but said the issue had been “troubling” him and it was time to speak out.

He made the unexpected attack on the culture of political correctness while campaigning for the Tories in Glasgow East.

It is a sign of the confidence Mr. Cameron now has — backed by consistent opinion poll leads of about 18 points — that he feels able to make such strong comments.

Last night, Labor sources said his remarks could provoke a negative reaction similar to that caused by John Major’s “back to basics” campaign.

Mr. Cameron dismissed that notion and said: “Of course as soon as a politician says this there is a clamor, ‘but what about all of you?’ Let me say now, yes, we are human, flawed, and frequently screw up.”

He toured the constituency with the former Tory leader, Iain Duncan Smith, who has carried out work for Mr. Cameron on how to repair what they regard as Britain’s “broken society.”

He said that as well as parents, head teachers, police officers, and businesses must help by taking responsibility for delivering results.