Children who live with both parents improve GCSE performance twice as fast as classmates living with just their mothers

Statistics showed 60 per cent of those from two-parent households gain five good GCSEs - up from 49 per cent in 1997.

In contrast, children living with just their mothers had only a 43 per cent GCSE success rate - up from 37 per cent ten years ago.

The figures were issued by Schools Minister Jim Knight in response to a written question from the Liberal Democrats.

They will reignite criticism of Labour's benefits system, which is said to penalise couples with children for staying together. A typical-couple on low or middle income would be £69 a week better off if they lived apart. In some cases the difference is £100.

The Tories have urged ministers to end the "couples penalty" - but there were also calls from the Lib Dems for the Government to do more to help disadvantaged families.

Scroll down for more ...

The gulf in exam results between children from two-parent and single-parent homes is widening, the figures showed.

They reinforced recent research which has underlined the importance of fathers in promoting children's achievement at school.

When he released the figures, Mr Knight admitted "complete information is not available." The latest statistics relate to the period from 1993 to 2003.

In 1993, 45 per cent who lived with a mother and father figure - including step-parents - gained five GCSEs at grades A* to C.

By 1997, this had reached 49 per cent and by 2003, it was 60 per cent.

Among those living with just their mother, only 34 per cent got five GCSEs in 1993, rising to 37 per cent by 1997 and 43 per cent by 2003.

LibDem education spokesman David Laws said: "These figures show the massive gap between children who come from well-supported families and affluent backgrounds and those from more disadvantaged and less stable backgrounds.

"This gap has grown hugely over the last decade.

"This shows that the Government needs to be doing more to target educational disadvantage and to support families."

Jill Kirby, director of the Centre for Policy Studies think-tank, said: "This is more evidence to show children's educational progress is affected by their home environment, and a home headed by two parents is more likely to provide the stability and support children need throughout education.

"This means the Government should give every encouragement for families to stay together and bring up children together.

"The problem with too much of our tax credit and welfare system is that it encourages the formation of separate households."

The trend emerged as a Sheffield University study showed children whose parents are socially active perform better in exams.

It found that mothers and fathers who are active in sports teams, charities and political parties tended to have higher-achieving children.