Gordon Brown has made social mobility a focus of his premiership
Labour's policies may be improving social mobility, according to a study published by the Prime Minister's Strategy Unit.
It examined the link between parents' earnings and academic achievement for children born in 1970 and 1990.
The study said the results "suggest a statistically significant decline in the importance of family background on educational attainment".
But the Conservatives said any improvements were "fractional" at best.
Gordon Brown has said increasing social mobility must be a "national crusade", but the prime minister has been accused of presiding over widening class and social divides.
Education charity the Sutton Trust has also claimed that the government's education policy fails to give poorer children the chance to improve their quality of life.
Figures published on Monday by the Strategy Unit suggest that, between 1970 and 2000, social mobility neither improved nor deteriorated.
However, findings provided for it by Bristol University, the London School of Economics and the Institute of Fiscal Studies seem to show that there have been encouraging signs since then.
They appear to indicate that a child's academic achievement - measured by the number of GCSEs they pass - is becoming less dependent on their family's wealth.
'Making a difference'
Cabinet Office minister Liam Byrne told the BBC: "Despite the changes of the 1970s, 1980s and 1990s, social mobility didn't get moving a lot.
"Now there's a sense that since 2000 we have been making a difference."
Mr Byrne said increased nursery places, improving exam results, more people staying on at school after the age of 16 and better on-the-job training meant poorer people's life chances were improving.
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For the Conservatives, shadow work and pensions secretary Chris Grayling said: "What a damning indictment of 11 years of Labour government - of vast amounts of money spent on regeneration programmes, on complex new systems of support for people on low incomes, on the New Deal - that the best they can claim is a fractional improvement.
"If indeed that fractional improvement even exists outside the Downing Street spin machine...
"The truth is that Britain today is a country where poverty is getting worse."
Mr Grayling is due to deliver a speech on social mobility later.
In June, Mr Brown said a white paper on on the subject would be published by the end of the year.