State school pupils may be lowering their chances of winning an Oxbridge place by applying for the most popular subjects.
Figures suggest that state-educated sixth-formers are more likely to apply for the most over-subscribed courses at the prestigious institutions than those who attend fee-paying schools, while privately educated youngsters are more likely to apply for the least over-subscribed.
One charity said that privately educated pupils may be "gaming the system", while private school leaders argued that they offer a wide range of subjects that are useful to many Oxbridge subjects.
Figures given to the Press Association show that last year, 30.7% of applications from UK state school students were for the five most over-subscribed subjects at Cambridge, compared to 28.4% of private school applications.
The five most over-subscribed subjects were Computer Science, Economics, Engineering, Psychological and Behavioural Studies, and Human, Social and Political Sciences.
In comparison, around a fifth (19.5%) of UK independent school applications were for Cambridge's five least over-subscribed subjects (Classics, Music, Modern Languages, History and Geography), compared to around one in eight (12.4%) of all state school applications.
Data published by Oxford shows that "state applicants' success rate is affected by subject choice" with UK students applying "disproportionately for the most over-subscribed subjects".
Between 2014 and 2016, on average, around a third (34%) of UK state school applications were for the prestigious institution's five most over-subscribed subjects (Economics and Management; Medicine; Philosophy, Politics and Economics (PPE); Law and Mathematics) compared to just over one in four (28%) of private school applications.
In addition, the university said, state school students apply in "disproportionately low numbers" for the least over-subscribed subjects (Classics, Music, Modern Languages, Chemistry and History).
Between 2014 and 2016, almost a quarter (24%) of applications from UK privately educated students were for these courses, compared to just 17% of all state school applications.
Sir Peter Lampl, chairman of social mobility charity the Sutton Trust, said: "It is concerning that state school pupils are more likely to choose subjects that are oversubscribed, reducing their chances of getting in.
"Students should choose the subject that's the best fit for them, rather than picking subjects to 'game the system'.
"It may be that independent schools are able to give better information and guidance about which course their pupils are likely to get in to.
"Universities and state schools have to work together to make sure all young people have the support they need to navigate the broad range of subjects on offer.
"State school students should have the same advice and guidance as those from independent schools when it comes to deciding which subjects to apply to."
But Peter Hamilton, of the Headmasters' and Headmistresses' Conference, which represents private school leaders, and head of Haberdashers' Aske's Boys' School in Hertfordshire, said that the figures are explained by the "range of sixth-form studies that different schools can offer and the breadth of high-level attainment that each school achieves".
"In independent schools we are fortunate to be able to offer students an exceptionally wide choice at A-level and Pre-U (specialist subject exams offered by one of Cambridge University's exam boards), as well as the International Baccalaureate," he said.
"These sixth-form studies map onto the same wide range of traditional subjects offered by Oxford and Cambridge, such as classics, music and modern languages.
"In recent years our colleagues in state schools have had to limit subject choice and increase class sizes because of austerity.
"This has had the effect of concentrating high attainment in state schools in a smaller set of disciplines which, in turn, generates high numbers of applications per place in certain Oxbridge subjects."
Dr Samina Khan, Oxford's director of undergraduate admissions and outreach, said: "Students from the state sector do tend to apply for Oxford's most competitive courses, as well as the more vocational courses.
"Much of our outreach work is aimed at giving state school students the best possible information and advice about both the Oxford admissions process and the range of careers open to Oxford graduates regardless of their chosen course."
Oxford received more than 19,000 applications last year and Cambridge around 16,750.
The figures come in the week that teenagers across England, Wales and Northern Ireland receive their A-level results.