The value of a university education has halved in the past 20 years, new research has shown, as critics claim that degrees have become "disqualifications".

The "graduate premium" is a term often used to refer to how much more graduates are likely to earn on average, compared to their peers who do not hold a degree.

The new study analysed how the financial return to a degree has changed over a 20-year period during which increasing numbers of people have been choosing to study at degree level.

Researchers found that graduates born in 1990 earned 11% more than non-graduates at age 26. However those born in 1970 earned 19% more than their peers who did not go to university. This suggests the "graduate premium" fell by eight percentage points during this period.