In
addition, almost 40pc of British children now live with either a single parent
(24 percent) or a cohabiting couple (14 percent).

Some 8,000 same-sex
couples now have children, the ONS figures
say, while almost 8 million people are living
alone.

The figures highlight
the continuing decline in popularity of marriage, despite studies showing that
it provides the most stable background for children.

The ONS’s bulletin,
published on Thursday, shows that in 2011 there were 17.9m families in
Britain.

Of these, 7.6m were
married or in civil partnerships and childless, while 4.5m had children under
16.

But although married
couples “are still the most common family type”, their number is declining as
more relationships break down and fewer couples choose to
wed.

Over the past decade
the number of married couples fell by 262,000 to 12m, while the number of
cohabiting couples rose from 2.1m to 2.9m.

The ONS said the
types of families with children “changed significantly” between 2001 and 2011,
with 62 per cent of children now living with married parents, 14 per cent with
cohabiting couples and 24 per cent with a single
parent.

The number of lone
parents with children has risen “steadily but significantly” from 1.7m to 1.96m,
rounded up to 2m by the ONS.

Almost all (92 per
cent) of these single parents were women: “Women are more likely to take the
main caring responsibilities for any children when relationships break down, and
therefore become lone parents.”

Increasing numbers of
same-sex couples are living together (63,000) and entering into civil
partnerships (59,000), with 8,000 said to have
children.

More couples had one
child rather than two or more in 2011 compared with a decade ago, but the ONS
said this could just be down to women “postponing their childbearing to older
ages”.

Overall, there were
26.3m households in Britain in 2011, up seven per cent since 2001 as a result of
immigration and people living in smaller units.

The proportion of
households containing just one person rose by some 700,000 over the past decade,
to reach 7.7m.

Among 16 to 64
year-olds, more men live alone as they are more likely to never marry. But over
65 the “pattern is reversed”, partly because women tend to live
longer.

Adults in the “1960s
baby boom generation”, aged 45 to 64, have fuelled the rise in the number of
single-person households in recent years as fewer people from that generation
have chosen to marry.