Poor teenagers are being put at a disadvantage by the current university application system, which relies heavily on predicted grades and personal statements, it has been suggested.
Bright teenagers from poor backgrounds are more likely to be predicted A-level grades lower than they actually achieve, according to a study published by the Sutton Trust.
This means that they can end up applying for degree courses with lower entry requirements than they are capable of getting.
At the same time, disadvantaged students are less likely to get help in preparing their personal statements, and to be able to provide many examples of their work and life experiences, it says.
The study, by Dr Gill Wyness of the UCL Institute of Education, calls for a major overhaul of the system, with youngsters applying for degree courses after they receive the results of their A-levels and other qualifications.
It says that official figures show that in 2016, the most advantaged university applicants were about six times more likely to go to a "high tariff" institution - those with the highest entry requirements - compared with the most disadvantaged.
"Though the UK's admissions process is highly centralised, the process is still complex, time-consuming, and requires young people to make potentially life-changing decisions far in advance of university entry," it says.
"Many of the elements of this process may put students from poorer backgrounds at a disadvantage."
Bright poor students lack the information, advice and guidance they need when applying to university, it says, which leads to many making "sub-optimal decisions when choosing their universities".
"Students must make their course choices based on predicted rather than actual A-level exam grades," the study says.
"Evidence shows that the majority of grades are over-predicted, which could encourage students to make more aspirational choices.
"However, high-attaining disadvantaged students are more likely to have their grades under-predicted than their richer counterparts.
"This could result in them applying to universities which are less selective than their credentials would permit."
About 1,000 disadvantaged, high-achieving students a year have their grades under-predicted, it says.
The study also warns: "Personal statements are a further barrier to entry for poorer students.
"Those from disadvantaged backgrounds are less likely to be supported in preparing these essays, and as such their statements tend to contain more grammatical and spelling errors.
"But those from deprived backgrounds are also able to provide fewer examples of the types of work and life experiences that many colleges and universities value, and use to decide between applicants."
Sutton Trust chairman Sir Peter Lampl, said: "Access to leading universities has improved and they are working hard to attract a wider applicant pool.
"However, the brightest disadvantaged students, given their grades, are under-represented at leading universities.
"The admission process itself may be responsible for this.
"Accordingly, the Sutton Trust is recommending we move to a post-qualification applications system.
"This is where students apply only after they have received their A-level results.
"This does away with predicted grades.
"Having actual grades on application empowers the student. They can pick the right course at the right university with a high degree of certainty they are making the right choice."
Sally Hunt, general secretary of the University and College Union, said: "This report highlights why the current system of students applying based on predictive grades is not fair.
"It is in everyone's interests to give all students the very best chance of fulfilling their potential and one huge step in the right direction would be to allow them to apply to university after they receive their results."