The union wants to ensure that black and female students do not face the possibility of prejudice by markers who identify gender or race from candidates' names.

The proposal is intended to ensure that women and students from ethinic minorities cannot be discriminated against in marking

Instead the union proposes that all assessed course work and exam papers should be considered using numbers rather than names, ensuring that no discrimination is possible.

"We're not saying that lecturers are racist or sexist, but that bias exists throughout society and sub-consciously it could affect marking. If universities adopted anonymous marking they could put themselves beyond reproach and remove any question of discrimination," said an NUS spokesman.

The union says that there have been suspicions about prejudice in marking at a number of universities, including the allocation of first class degrees, and that anonymous marking would prevent this.

Sir Herman Ouseley says anonymous marking is a "simple step" to reduce the risk of prejudice

At present universities vary in the level of anonymity in marking students' work. There are universities in which formal exam papers are anonymous but assessed coursework is identifiable, others provide anonymity for undergraduates but not postgraduates and others provide anonymity in all marking.

The campaign has been supported by Sir Herman Ouseley, Chairman of the Commission for Racial Equality, who says that anonymous marking "is a very simple step which could be easily taken and which would help universities better deliver an educational service which does not discriminate".

Julie Mellor, Chair of the Equal Opportunities Commission, also says that the measure would "remove possible bias".