Three unions raised concerns over alleged racism and equalities in the Science Policy Research Unit (SPRU).
The unions said the letter was to address ‘tackling inequality in SPRU and campus-wide’.
The letter to the human resources department, from the University and College Union (UCU), Unison and Unite, said: “We believe SPRU has only ever appointed white members to its executive committees.
“White members of staff appear to progress via regular promotions in a way which seems unavailable to black and minority ethnic members of staff.
“Could you please provide as a matter of urgency monitoring data listed by grade since 2002 and disaggregated by ethnicity? Also copies of Equality Impact Assessments conducted on any of the functions of the SPRU.”
The unions also asked the university to eliminate discrimination and advance equality of opportunity at the SPRU.
The letter asks for a meeting with university bosses to ‘discuss the issue of equality across the university’.
Sheila Gupta, the university’s director of human resources, said: “This week the university has launched a new equality, diversity and inclusion strategy – titled Inclusive Sussex.
“Becoming an institution that leads the way in terms of equality sits at the very heart of the University’s future.
“It would be unethical to disclose the ethnicity of applicants for senior roles in past appointments.
“The university will be signing up to the Equality Challenge Unit’s Race Equality Charter this year which will start an extensive programme of work to improve the representation, progression and success of minority ethnic staff and students within our organisation.
“The university is in regular dialogue with all relevant unions and welcomes ongoing discussions about equality, diversity and inclusion – we must keep working together.”
The university responded to the allegations of racism and said: “The university is not able to comment on individual HR matters due to confidentiality and data protection reasons.
“A detailed and thorough investigation was conducted following an allegation of racism – which was not upheld.”
The letter to the University of Sussex from the unions can be read in full at: ucusussex.wixsite.com/ucusussex/campaigns