Strengthening families is essential to creating strong societies and tackling poverty, Iain Duncan Smith has said.

The Secretary of State for Work and Pensions said that although recent years had started to see "real change" in the discourse on marriage, it had been tough to speak in support of marriage at the political level where it was not seen as "fashionable".

"Doing so has often meant being something of a lone voice – at least within the political sphere – where, over the years, the political establishment came to frown even at the mere mention of marriage," he said.

"I believe any government serious about tackling poverty and promoting a strong, cohesive society must seek to strengthen families.

"And yet, when a politician extolled the virtues of the fundamental institution of marriage, too often, it has been taken to mean that they are attacking those whose lifestyles don't fit.

"This is an absurd and damaging assumption.

"Support for society's most successful institution does not mean that you cannot also be sympathetic to, and supportive of, families where one parent is left with the difficult responsibility of bringing up children."

Mr Duncan Smith made the comments during a speech at the Marriage Foundation's conference this week.

He criticised penalties on couples in the benefits system as "perverse" and contended that the "default should be set at an even balance".

"In the welfare system – as in the court and tax systems – where the default has been set against couples, the risk is that it entrenches a process of family breakdown," he said.

With the number of children from lowest income families not living with both parents set to rise in the next five years, he said society must no longer be afraid to talk about these issues.

"Not as a 'finger wagging' exercise, as has sometimes happened in the past – for government has no place judging peoples' relationships.

"But we do have a duty both to level the playing field – for too long tilted against marriage – and to do all we can to support the sustained and healthy parental relationships that matter most, providing a nurturing environment and giving children the best possible start in life."

He went on to say it was an "important moment in reversing the bias against marriage".

"For the evidence shows that cohabitation and marriage are two different relationships.

"We know that cohabiting parents are around four times more likely to have separated by the time a child is three.

"And by the child's fifth birthday, more than one in four of those who cohabit have split up, whereas for married parents the break-up rate is fewer than one in 10 … one tends to have greater longevity and stability than the other."

Despite the frequency of marriage breakdown, Mr Duncan Smith pointed to research showing that three quarters of people below the age of 35 still see marriage as one of their primary aspirations in life.

However, with only 57% of people by the age of 35 being married, he said more needed to be done to find out what was stopping more young people from marrying and remove the barriers standing in their way.

Young couples should also be given more access to marriage preparation and relationships education, he contended, saying that too many had an "unrealistic expectation of what married life will be like, in some cases an almost fairytale view".

"Reinforced by celebrity culture and the glossy spreads in Hello! Magazine, the focus is too often overwhelmingly on the ceremony itself – by some estimates costing an unbelievable £20,000 on average, with some couples getting into debt just to meet the costs.

"Starting married life with a large overhang of debt, but without the understanding that marriage requires compromise to overcome real challenges.

"All of this puts huge pressure on newly married couples from the start.

"What seems to have been forgotten is that the point of marriage is love, commitment, and creating a stable environment in which to bring up a family.

"None of these cost more than the price of a marriage licence."

The Government is currently conducting a Family Stability Review into current levels of support for married couples across different departments and agencies. The review is expected to report next year.