Asian and black students on full-time PhD programmes are 10 per cent less likely to complete their doctorates in ten years than white students, according to a separate report on overall entry and completion rates.
The report, updating an earlier study, is the first to include ethnicity and disability data.
Asian and black students' completion rate was 67 per cent versus 76 per cent for whites.
"This is a significant finding and one we take very seriously," said Phil Hubbard of Hefce, Overall, 57 per cent of students who began a fulltime PhD in 1996- 97 finished in five years, rising to 72 per cent after seven years and 76 per cent after ten. Of part-time students, 48 per cent completed in ten years.
The report said disability had no impact on completion rates.