Marriage is set for a steep decline in the next 25 years, while the rate of cohabitation is set to soar, according to 
UK statisticians.
The number of adults who do not get married is set to rise by almost half, while it is thought the number of cohabiting couples will rise by 65 per cent, according to projections made by the UK’s Office of National Statistics on Wednesday.
Pro-family campaigners said the trend presents a “bleak picture” and warned children are likely to suffer as they will be at more risk of being in a less stable household.
The figures are set to increase worries that traditional families are being weakened, as proposed changes giving unmarried couples the same rights as married ones in several areas of law and benefits are suggested by the UK’s Law Commission.
The projections come after Conservative pledges to strengthen marriage through the tax and welfare system were left out of the programme for the new Conservative/Liberal government.
The ONS figures also indicate that middle aged women in particular will see a sharp change, with numbers not married trebling by 2033.
The projections suggest a changing face for the average household as separate figures also showed up to a third of children now live with just one parent.
And an expanding older generation means the number of pensioners who are divorced is set to double.
In 2008 there were 15.3 million people in England and Wales who had never married – making up 35 per cent of the adult population.
In contrast, 21.7 million – or 49 per cent – were married. The figures excluded those who are divorced or widowed.
But projections by the Office for National Statistics suggest that by 2033 some 22.7 million people will not have married compared with 22.2 million who will have.
It means within 25 years, accounting for population growth, some 43 per cent of adults will have never married compared with just 42 per cent who are in wedlock.
Among those who will have not married by 2033 will be 3.8 million couples who live together, the ONS suggests, which will be a two thirds rise on the current 2.3 million cohabiting households.
Anastasia de Waal, the director of family and education at Civitas, a think tank, said: “It is a bleak picture.
We know that cohabiting in this country does not reflect marriage and is less stable marriage.
“If we see a proliferation of cohabiting then we will see a decline in stable relationships and that has major implications for children, who are more likely to face separation.
“The picture is not a happy one if this is the case.”
The figures were published alongside the ONS Population Trends document, which revealed 30 per cent of dependent children live in a home where there is only one parent.
It is the equivalent of 3.8 million children in a lone parent household or where parents live apart or have new partners.
Hugh McKinney, of the National Family Campaign, said: “Time is running out for the family.
“Successive governments have ensured that the focus on the family has changed from marriage to non-marriage and it is about time that the balance was redressed.”
Last year, the Law Commission, the Government’s law advisers, proposed that unmarried couples who live together for two years will be automatically entitled to half their partner’s estate if they die without a will.
The move would end rules dating back more than 80 years, and give most partners who do not marry the same rights as bereaved spouses.