Speaking at a fringe event at the Conservative Party conference in Manchester, the Tory MP also claimed cohabiting couples have “inherently unstable” relationships.

He went on to claim men out of wedlock were “released to do all the things they wouldn’t normally do” such as committing crimes, drinking too much, taking drugs and fathering multiple children.

Couples living together were more likely to break up as the arrangement “suits the man” more than the woman, he went on to claim, and if men were not taught of the importance of marriage they would develop “low value for women” and seek out “the alternative on the internet”.

“Cohabitation is a very different relationship from marriage,” he said. “It is inherently unstable. The level of breakup is staggering high compared to marriage, and for the most part, these relationships break up upon arrival of a child.”

He went on: “The answer I think is because cohabitation suits one of the partners more than the other. Almost invariably it suits the man, because they have to make good on their commitment and when that commitment is facing them they then withdraw.

“In marriage, having made that commitment, the child becomes a focus for your responsibility and you commit more. They commit automatically once the child arrives.”

He went on: “Out there, these boys particularly, when left without the concept of what [marriage/commitment] is about will find the alternative on the internet.

“And the alternative on the internet, now so readily available, is about abusive sex and low value for women. That is where they will go.

That’s why, certainly at the bottom end of the income scale, there is such collapse of self-worth among young girls because they see themselves as objects because they are taught from the beginning that is the only way to get a man.”

He said men “unanchored” from a partner were more likely to get into debt and commit crimes, adding: “What has been going on all these years is the men that have been absent from these families in many of these low income groups are now a problem.

“They are out, no longer having to bring something in for their family, so they can be released to do all the things they wouldn’t normally do and shouldn’t do, so levels of addiction, levels of high criminal activity, issues around dysfunctional behaviour, multiple parenting – all those things are as a result of the un-anchoring of the young man to a responsibility that keeps them stable and eventually makes them more happy.”

The former Work and Pensions Secretary, who introduced Universal Credit, said there was a “family breakdown crisis” in Britain among lower income groups, but “middle class opinion” meant ministers were “scared stiff” of tackling it.

He cited research by the Centre for Social Justice, the think tank he founded and of which he is chairman, that found that teenagers from the poorest 20% of households were 65% more likely to experience family breakdown than teenagers in the top 20% of households.

He said one in five dependent children had no father figure at home, and added: “A child in Britain is more likely to experience family breakdown than anywhere else in the world, not the western world, the world.”

He compared marriage to buying into a golf club membership, which would see men sign up for “absurd things” and claimed the current system financially rewarded single people.

Duncan Smith said: “If something really matters to you in life, you commit to it. People join golf clubs and they sign up for the most absurd things that you have to do, wearing trousers, shoes, all sorts of things.

“They will sign up to all of that. They will sign contracts on housing, they will do financial contracts that they will sign and never question.

“On the most important relationship in our lives, the thing that will damage or make us, family formation, we let the middle class sit there and tell us this is a lifestyle choice, and we shouldn’t ever tell people that it matters that you make an absolute commitment such that it is written down on a piece of paper.

“Education is critical.”

He added: “We don’t ask for special privileges for marriage and stable families, we simply ask to get that pendulum back in the middle so that people who make a choice do not have to make a choice that is financially damaging rather than benefiting.

“The whole system is set up to reward those living by themselves and essentially penalise those who stay together, because they get more money.

“If you are on a very low income and the choice is between, basically, losing money or gaining money, ultimately you will choose the path of gaining money because that is how it works.”

The fringe event was the only one at the party conference discussing family breakdown, he said, before adding: “The truth is I sit in a building where people are scared stiff of this subject.”

Sir Paul Coleridge, chairman of the Marriage Foundation, also spoke at the event.

He said: “The problem is that there is a view out there, borne of ignorance I’m afraid, that all cohabiting relationships are of equal worth, of equal value, of equal stability. I’m afraid they are not.”

Marriage means a relationship three times more likely to last until a child is into their teenage years, he said.

“I think a very straightforward message from the government through the tax system, like recycling your rubbish or anything else, it is the message that you send to people; that one form of a committed relationship is more valuable and useful to society than another.”

He said men not in marriage were more likely to die earlier, experience health problems and get into debt.