It is wrong to equate marriage and cohabitation, a leading member of the UK Government has said.

The Secretary for Work and Pensions, and former Tory Party leader, Iain Duncan Smith, said that the Coalition government should fight to protect the traditional family, which he called ‘the most vital part of society’.

Mr Duncan Smith warned that failure to support marriage would lead to further social breakdown, and blamed broken homes for funnelling children into the gangs that ran rampant during the summer riots, according to The Daily Mail.

And he reminded people of the Government’s pledge to introduce tax breaks for married couples before the next election, arguing that politicians should not be ‘neutral’ about which kinds of families are best for the country.

In a speech in honour of the late Tory peer and family campaigner Janet Young, he delivered his most outspoken remarks yet about why it is better for couples to marry.

‘It is important to understand that there is a difference between cohabiting and marriage,’ he said. ‘People will make their own choices about their relationships, but they should understand what those choices are. The relationships are not the same – and there are consequences for us all.’

Marriage rates have more than halved in the last 40 years, while the number of lone-parent households has increased by an average of 26,000 a year over the past 30 years.

Mr Duncan Smith warned: ‘At the heart of so much social breakdown sits the collapse of a forgotten institution. That institution is the family, and it is absolutely fundamental to a stable society.

‘Strong families are where children pick up their basic values, learn the difference between right and wrong, and understand the value of loving and committed relationships.’ He pointed out that studies have shown about one in 11 married couples split up before their child’s fifth birthday, compared with one in three unmarried ones.

Mr Duncan Smith added that children who do not grow up in a two-parent family were 75 per cent more likely to fail at school, 70 per cent more likely to become addicted to drugs and 50 per cent more likely to have an alcohol problem.

‘Some still say that we must be neutral towards family life,’ he said. ‘But they are wrong. You cannot be neutral when the system you inherited is already so anti-family.

‘We will have to fight to ensure that the Government leaves a strong legacy on the family. After all, family is the most vital part of society.’

Mr Duncan Smith also delivered a withering verdict on the recent Norgrove report into the future of family courts, which ruled out giving fathers or grandparents any legal rights to see children.

He condemned the court system ‘which, like far too many institutions of the State, seems to have forgotten the importance of the father and the extended family’.

Taking on the social work establishment that believes all family structures are as good as each other, he said: ‘There is nothing progressive about having children growing up in broken and abusive homes, many of whom go to primary school unable to speak, are excluded from secondary school and then find themselves next on the gang leaders’ recruitment list.’

Fiona Weir, chief executive of single parents charity Gingerbread, criticised the tone of the remarks.

She told The Daily Mail: ‘The vast majority of children growing up in single-parent families do so healthily and happily. Families need more support to help them handle conflict, and more protection from financial hardship. They don’t need government finger-wagging.’

And last month Lord Tebbit, the party’s former chairman, questioned the Government’s approach on the issue.