Four in 10 of the country's leading professionals also attended private schools, with 10 top independent schools producing 12 per cent of the group, according to a report by the Sutton Trust.
The charity, which seeks to promote social mobility, compiled information on the educational backgrounds of nearly 8,000 people who appeared in the birthday lists of national and Sunday newspapers during 2011.
Of these people, 31 per cent went to Oxbridge, a further 20 per cent attended a leading research-intensive university and 22 per cent did not go to university.
Analysis of the list shows the profession most dominated by Oxbridge graduates is the diplomatic service at 62 per cent, followed by law at 58 per cent, the civil service at 55 per cent, education and literature at 48 per cent and financial services or the City at 47 per cent.
The report also found that 44 per cent of those surveyed attended private schools, despite such independent institutions accounting for just 7 per cent of all school places.
Eton College alone produced 330 leading people - 4 per cent of those surveyed.
The top comprehensive schools - with six leading professionals each on the list - are Haverstock School, in north London, attended by Ed and David Miliband and Holland Park School, attended by former Labour Cabinet minister Hilary Benn.
Sir Peter Lampl, chair of the Sutton Trust, said: "Studies like this show how far we still need to go to improve social mobility in this country and ensure that every young person can achieve his or her potential, regardless of their family background."