Boris Johnson's most senior black adviser to step down in May
Samuel Kasumu will leave his post as special adviser for civil society and communities in May.
The news comes a day after a government-backed review of racial disparities in Britain
was published.
Commission on Race and Ethnic Disparities' 258-page report was criticised for being "steeped in denial".
But a Number 10 spokesman rejected reports that Mr Kasumu's resignation, first reported by Politico, was linked to this.
"Mr Kasumu has played an incredibly valuable role during his time at No 10," he said.
"As he previously set out, he will be leaving government in May - this has been his plan for several months and has not changed.