In 2007, the proportion of children achieving five good GCSEs, including English and maths, in schools where more than half of the pupils were eligible for free school meals was 13 per cent, a drop from 14 per cent in 2006.
In contrast, at schools where less than one in 10 pupils were eligible for free school meals, the proportion achieving five good GCSEs, including English and maths, rose from 57 per cent in 2006 to 58 per cent in 2007.
This means that the gap has widened by two percentage points in the space of a year, from 43 per cent in 2006, to 45 per cent in 2007.
Shadow children's secretary Michael Gove, who obtained the figures in answer to a parliamentary question, said: "The gap between children from schools in deprived areas and wealthy areas is widening.
"Parents and children, particularly those from deprived backgrounds, are being let down by this block on opportunity."
Children's minister Baroness Morgan said: "More children on free school meals get five GCSE A*-Cs than a decade ago and 2008 saw a further two percentage point improvement in their achievement."
She said two initiatives, the Narrowing the Gaps strategy and the Extra Mile project would help with improvement.
She added: "This is a complex and challenging issue but no-one should be in any doubt that it is one we are tackling head on." (telegraph.co.uk 8:04PM GMT 04 Jan 2009)