Oxford and Cambridge should found more colleges to help boost the numbers of disadvantaged students at the prestigious universities, it has been suggested.
In recent decades, other universities have expanded much more than Oxbridge, and such a move would give more youngsters from under-represented groups the chance to attend, according to Nick Hillman, director of the Higher Education Policy Institute (HEPI).
The suggestion is included in a new paper published by the HEPI and the charity Brightside which puts forward ideas and advice on widening access to higher education for the new universities regulator, the Office for Students (OfS), and the new director for fair access and participation, Chris Millward.
Other proposals include looking again at post-qualification admissions, and appointing a commissioner for student mental health.
In the paper, Mr Hillman suggests that higher education "benefits enormously from the presence of Oxford and Cambridge", arguing that "as two of the oldest, most prestigious and most successful universities in the world, the whole system sees trickle-down benefits".
But he goes on to say that thought is needed about making access to the UK's most selective institutions, such as Oxbridge, fairer, alongside widening participation overall.
"Fortunately, the best solution to both challenges is the same: provide more places, so that entry is not such a fierce battle," Mr Hillman says.
"In recent decades, other institutions have expanded their undergraduate numbers far more than the two Oxbridge institutions have done.
"If existing colleges are reluctant to increase their undergraduate entry, then it is time to consider founding a number of entirely new Oxbridge colleges to boost the number of students from underrepresented groups at our oldest, richest and most prestigious universities."
The two institutions have faced criticism in the past over access, with some critics arguing that they could do more to boost the numbers of disadvantaged students applying for, and taking up, places.
Both operate a collegiate system, whereby students are typically members of an autonomous college within the overall university.
Post-qualification admissions to university
Conor Ryan, of the Sutton Trust charity, argues that the director for fair access should "reopen the debate on post-qualification admissions"
This involves students applying for degree places after they have their exam results, rather than the current system, which uses predicted grades.
Mr Ryan said that Sutton Trust research found that bright but poor students "consistently have their grades underestimated", adding that "without AS-levels, the time is ripe for change".
Ross Renton, pro-vice chancellor of the University of Worcester, calls for the appointment of a commission for student mental health, noting that there has been an increase in the numbers of first-year students disclosing mental health problems, and arguing that supporting students dealing with these issues should be a priority.
An Oxford University spokeswoman said: "There are no plans to expand overall undergraduate numbers or create new colleges.
"Neither would be a straightforward process: Oxford is made up of around 40 colleges and permanent private halls, which already face major accommodation and other resource challenges.
"There are already many other college and university initiatives which are expanding the number of students from under-represented backgrounds."