Babies born out of wedlock rise by a fifth

Last year 327,000 children were born out of wedlock, 59,000 more than in 2001.

The proportion is pushing remorselessly towards half of all babies. Last year, 43.7 per cent of babies had unmarried mothers, compared with 42.9 per cent the year before.

But even these figures, revealed by the Office for National Statistics yesterday, do not show the full extent of the trend, which is skewed by the arrival of high numbers of migrants who traditionally have more children than British residents and are more likely to do so within marriage.

Campaigners yesterday linked the rise to Gordon Brown's tax credit system, which is far more generous to single parents than to couples.

They also blamed the continuing decline in the status of marriage and worries about the cost of divorce, heightened by big money court settlements.

Academic Patricia Morgan, author of a series of studies on family breakdown, said: "Tax credits have played a big part.

"Two out of three of the babies outside marriage will have been born to couples with one eye on the benefit authorities. There is strong state incentivisation of lone parenthood."

Earlier this month former Labour welfare minister Frank Field condemned the 'brutal neglect' of two-parent families in the benefits system.

His research showed that a single mother with two children under 11 on the minimum wage received tax credits last year that took her weekly income to £487 if she worked only 16 hours a week.

But a two-parent family with one earner would have to put in 116 hours of work on the same pay to get the same money.

Children born to unmarried couples are far more likely to end up in single-parent families than those born within marriage. A typical cohabitation lasts three years, while marriages average 11 years.