There is an "unexplained difference" between the achievement of some ethnic minority university students and their white counterparts, researchers say.
Getting a good grade degree increases earning potential
Black and Asian undergraduates are less likely to get a first class degree than white students, their study confirms.
The Department for Education and Skills team found the attainment gap remained even if factors like social background and prior achievement were considered.
The gap was widest for black Caribbean, black African and Chinese students.
The team used a statistical model based on a number of characteristics to predict what class of degree 65,000 undergraduate entrants would get.
This allowed for students' socio-economic background, prior academic achievement, subject of study, age and the type of higher education institution they attended to be considered alongside their ethnicity.
They predicted only 3% of black Caribbean and other black students, 4% of black African and 5% of Bangladeshi and Pakistani students obtained firsts.
This compared to some 13% of those termed white UK Irish and 16% of other white students.
The team said: "Even after controlling for the majority of factors we could expect to have an impact on attainment, being from a minority ethnic group is still statistically significant in explaining final attainment, although the gap has been significantly reduced."
The researchers concluded there was still "an unexplained difference" between students from white communities and those from ethnic minority groups.
They said: "These results potentially have quite serious implications. A number of studies have found that attaining a 'good' degree carries a premium in the labour market, and that this premium has been increasing over time."
But they added that their findings do not "automatically imply" that there is "some form of ethnic bias within the HE system".
Instead, a number of other factors, for which no information was available for the pupils included in the study, could explain the result.
"These include term-time working, parental income and education, English as an additional language and prior institution attended," they said.
The team suggested that, had these factors been taken into account, the attainment gap might have been reduced.
"However, it is difficult to judge the extent of that reduction, or whether or not it would have been eliminated entirely," it added.
Higher Education Minister Bill Rammell said the government was still committed to ensuring people from all backgrounds and all sections of society have the opportunity to benefit from and thrive in higher education.
"That is why we undertook this research and why we have already asked the Higher Education Academy and Equality Challenge Unit to start immediate follow up work with higher education institutions, to investigate these results further.
"We have to ensure that every student regardless of race or sex is given equal opportunity to succeed within higher education. This is both a social and economic necessity."
Underachievement of black schoolchildren, particularly boys, has long been a concern for ministers and community leaders.
But black youngsters have started to close the gap in educational performance on their white classmates at GCSE level.