Research from Business in the Community (BITC) found workers of Caribbean heritage in professional roles face an average pay gap of £3,814 compared to their colleagues - the highest pay gap of any ethnic group.
More than half of the Caribbean workers surveyed (55%) felt they weren't being paid enough for the work that they do, despite almost three quarters (72%) having diplomas, degrees, PhDs or Masters.
Ethnicity pay gap in the workplace:
A third of those asked said having a mentor would help them overcome obstacles in the workplace, yet only 14% had access to one.
Speaking to HR magazine Sandra Kerr, race director at BITC, said: "Reciprocal mentoring is a great way for leaders and allies in the workplace to collaborate and engage with their colleagues. If more employers were to provide mentors or step into the role themselves, we would see workplaces taking a step closer toward equality.
"There is no clear answer as to why there are not enough mentors available for the employees who want them, but this is an issue that employers can tackle."
The survey also showed a lack of representation for ethnic minorities at senior level, as only 3% of respondents were in senior higher paid roles.
This was supported by the Multicultural Britain study from Opinium this week which found 36% of ethnic minorities felt their senior leadership was less diverse than the overall team.
Kerr stressed the importance of pay gap reporting to try and address such issues.
She added: "To address this unacceptable pay gap, the government must make ethnicity pay gap reporting mandatory. Publishing this data ensures transparency but it also helps employers ensure that action is directed to where it is needed most.
"Businesses have been clear, they want to see mandatory ethnicity pay gap reporting introduced as they see it a tool to create fair workplaces rather than a burden."
BITC surveyed 779 UK employees from Caribbean backgrounds. Opinium's Multicultural Britain study surveyed 2000 UK adults between January and February 2022.