The number of British children being brought up by unmarried couples has doubled to almost 2 million since the 
mid-1990s.
New data from the Office for National Statistics dating back to 1996 show that, while the number of married couples bringing up children has dropped by almost 12 per cent to 4.6 million in that time, the number of unmarried couples living together has doubled to 1.8 million.
Because married couples tend to have more children than other types of family, six out of 10 children in Britain are still being brought up by married parent, The Daily Telegraph reports.
But in 1996 the proportion was almost three-quarters.
Meanwhile the number of lone parent families has grown by a quarter to almost two million.
There are now a million more people living alone than there were in 1996 – accounting for almost a third of all households.
And the economic downturn has sparked a rise in the number of households in which two or more families are living under the same roof to share the expense.
The ONS said the shifts were “statistically significant” pointing to a major long-term shift.
Christian Guy, managing director, of the Centre for Social Justice – the think tank/think-tank founded by the work and pensions secretary Iain Duncan Smith – said it was clear that family breakdown had reached “unprecedented” levels in the last few decades.
“These figures reveal growing levels of family instability and breakdown which should raise the alarm,” he said.
“We shouldn’t simply assume this is all inevitable. We have a lot more to do to promote stable families and provide the surest foundation in life for adults and children.
“If we don’t back marriage and commitment by saying they matter, these trends will continue.
“We spend a lot of money and effort picking up the pieces of family breakdown but virtually nothing preventing it.”
Meanwhile there are now 135,000 same-sex couples in the UK, including those in civil partnerships.
Twelve thousand of these couples have children.