'Rich thick kids' are doing better than 'poor clever children' before they start school due to accident of birth, Michael Gove has said.
The Education Secretary said urgent action is needed to close the attainment gap between rich and poor, which widens as youngsters move through the school system.
Speaking at a Commons education select committee, Mr Gove cited research conducted by Leon Feinstein at the Institute of Education which showed that children from wealthy backgrounds with low abilities overtake children from poor backgrounds with high abilities at a young age.
"So, in effect, rich thick kids do better than poor clever children and when they arrive at school, the situation as they go through gets worse," Mr Gove said.
He added: "Schools really should be engines of social mobility that overcome the disadvantage of birth, but unfortunately, at the moment, despite the best efforts of many, many people, the situation gets worse. That's why we need early intervention."
The research, which looked at the abilities of children born in 1970, found that social class was "strongly associated" with development during the early years.
Mr Gove told the cross-party group of MPs that out of 57 countries, Britain came second from bottom in terms of the level of education equality achieved. His comments came as the Department for Education announced an new independent commission into early intervention - which will look at how to give children from disadvantaged backgrounds the best start.
The inquiry will be chaired by Graham Allen, Labour MP for Nottingham North.
Mr Allen said: "I am taking on this added burden not for sectional interest or to score political points but to improve the life chances for people in constituencies like mine. Nottingham has proved we can intervene successfully. Now we not only need to prove we can take early intervention to a national level, we also need to find inventive ways to fund it in a time of economic drought."
In a wide-ranging committee meeting, Mr Gove was also asked about his decision to cancel the £55 billion Building Schools for the Future programme. He replied: "When I made the announcement, I did so after a great deal of thought, and it wasn't an easy announcement to make, because, inevitably, I was in the business of disappointing hopes."