Image caption Universities have to draw up plans for how they will attract a wide range of students

Universities should not be forced to "undo the problems of 18 years of upbringing and education", independent school heads have been told.

Peter Cottam, chairman of independent heads group, SHMIS, said skewing admissions towards state pupils is tackling the issue from the wrong end.

Admissions tutors often take account of pupils' backgrounds when making offers.

They can ask for lower A-level grades from poor pupils with potential.

Although this practice has been going on for many years, universities preparing to charge higher tuition fees are having to set out exactly how they will recruit from underrepresented groups - such as disabled, ethnic minority and disadvantaged pupils - as they draw up access agreements with the Office for Fair Access.

These can also include waiving tuition fees, outreach work and scholarship programmes, as well as lower offers for brighter pupils.

At the moment just over 7% of pupils in England go to private schools (more attend in sixth form) but they make up about half of those at Oxford and Cambridge.

And according to the Sutton Trust charity, only 2% of students at the 25 most selective universities were eligible for free school meals - a measure of deprivation.

Mr Cottam was speaking in Telford on Monday afternoon at the annual conference of the Society of Headmasters and Headmistresses of Independent Schools, which represents 100 independent schools.

He likened pressuring universities to undo social imbalances in their intakes to trying to improve "the design of an aircraft after it has already crashed".

'Blot on system'

He describe the "debate about the significant representation - or as Mr Clegg would have it 'the over-representation' - of our pupils in the most selective universities" as "carping".

He added: "It is a blot both on our educational system and on our society that so few young people from deprived backgrounds manage to fulfil their educational potential.

"It is not a good enough response to say that life is unfair. It certainly is sometimes and not just in education, and not just limited to those from socially and economically deprived backgrounds.

"But putting this right will not be easy. There is no silver bullet and it will take a great deal of time and effort because so many factors are involved."

"Discriminating against independent school pupils using a mechanistic template will not solve the problem, and it will also be unfair," he said.

"It sometimes feels as though our critics believe that the academic success of many of our pupils has either been handed to them on a plate or drilled into them and does not reflect any real ability or potential," he added.

'Narrow approach'

In January, Simon Hughes, the deputy leader of the Liberal Democrats and the government's adviser on access to higher education, called for universities to drastically limit their intake of privately education pupils.

But Mr Cottam, a head teacher at fee-paying Halliford School in Middlesex, said the argument about making lower offers to state school pupils is based on research that shows pupils educated in the state sector tend to do better at university than independent school pupils entering with similar grades.

He argued that there are a number of studies which have different results.

One suggests there is no difference in the performance of pupils from each sector, while another suggests independent school pupils do better, he said.

Nicola Dandridge, chief executive of Universities UK, said: "Universities already make strenuous efforts to seek out potential by looking at a number of factors when selecting students.

"Admissions decisions have to be based both on students' existing achievements as well as their likely future achievements.

"In terms of the most selective courses, it remains the case that some under-represented students often do not have the grades required. It is therefore critical that the sector continues its outreach work with schools, as well as working with young people to raise their aspirations and their awareness about higher education."

He also said that a "league table-dominated curriculum" has fostered a "narrow, utilitarian approach to education".

"One of the consequences, albeit unintended, of our current system is that education at secondary level has become too utilitarian and too exam-focused, with the result that it is far more difficult to engender a sense of intellectual excitement and adventure and to encourage one's pupils to take intellectual risks," he said.