Bruce Charlton, an evolutionary psychiatrist at Newcastle University, has written a paper asserting the reason why fewer students from poor families are admitted to Oxford or Cambridge is not because of social prejudice, but lack of ability.
He suggests that low numbers of working-class students at elite universities is the "natural outcome" of "substantial" IQ differences between classes.
He told The Scotsman yesterday, in an interview conducted by e-mail at his insistence: "Poor people have lower average IQ than wealthier people... and this means that a much smaller percentage of working-class people than professional-class people will be able to reach the normal entrance requirements of the most selective universities."
Dr Charlton said the average child from the highest social class is up to 30 times more likely to qualify for admission to a highly selective university than the average child from the lowest social class.
His claims could trigger an outcry similar to that faced by the Nobel prize-winning geneticist James Watson, who was forced to apologise after claiming that African and Caribbean workers were "demonstrably less able" than white ones.
However, Dr Charlton argues it is precisely the fear of creating controversy that prevents other academics taking the same line.
He said: "That is why such obvious scientific truths have not so far been stated clearly, or have actually been denied.
"(This theory is] accepted among those who know and understand the research."
He goes on to question the government's drive to get more students from poor backgrounds into top universities.
"The UK government has spent a great deal of time and effort in asserting that universities, especially Oxford and Cambridge, are unfairly excluding people from low social-class backgrounds and privileging those from higher social classes. Yet in all this debate, a simple and vital fact has been missed: higher social classes have a significantly higher average IQ than lower social classes."
Ministers insist the debate should be focused on helping young people realise their potential. Bill Rammell, Westminster's higher education minister, said: "These arguments have a definite tone of 'people should know their place'.
"There are young people with talent, ability and the potential to benefit from higher education who do not currently do so. That should concern us all."
Sally Hunt, general-secretary of the University and College Union, warned: "It should come as little surprise that people who enjoy a more privileged upbringing have a better start in life."
IQ, OR intelligence quotient, measures the ability to perform abstract reasoning and speed of learning.
But a debate rages over whether IQ tests are completely accurate and if their results are a reliable indicator of somebody's true level of intelligence.
Although tests may assess analytical and verbal aptitude well, they are not an accurate test of creativity, practical knowledge and other skills involved in problem-solving.
Many see IQ tests as an assessment of an individual's problem-solving ability, rather than general intelligence.
Others argue that they just show how good the individual is at IQ tests, especially during childhood.