The prime minister's most senior black adviser is to step down from his role in Number 10.
Samuel Kasumu will leave his post as Boris Johnson's 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.
The 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.
"Any suggestion that this decision has been made this week or that this is linked to the CRED report is completely inaccurate."
According to Politico, he told colleagues of his decision on Tuesday morning, just as the findings of the report were released.
Mr Kasumu will stay in post until May to continue work on improving the uptake of coronavirus vaccines among minority groups, its report added.
Asked about his departure, the PM said Mr Kasumu had "done some great stuff" in Number 10.
"I thank him very much, particularly on helping to encourage vaccine take-up amongst more hesitant groups and communities. And, actually, we're seeing some real success there," Mr Johnson said.
The PM described the report as a "very interesting piece of work" and said the government would be responding to it in "due course".
"I don't say the government is going to agree with absolutely everything in it, but it has some original and stimulating work in it that I think people need to read and to consider," Mr Johnson said.
He continued: "There are very serious issues that our society faces to do with racism that we need to address.
"We've got to do more to fix it. We need to understand the severity of the problem."
According to the BBC, Mr Kasumu drafted and retracted a resignation letter in February, in which he accused the Conservatives of pursuing "a politics steeped in division" and suggested Kemi Badenoch, the equalities minister, may have been in breach of the ministerial code over her row with a journalist.
Labour's shadow women and equalities secretary Marsha de Cordova said: "To have your most senior advisor on ethnic minorities quit as you publish a so-called landmark report on race in the UK is telling of how far removed the Tories are from the everyday lived experiences of black, Asian and ethnic minority people.
"Their divisive report appears to glorify slavery and suggests that institutional racism does not exist despite the evidence to the contrary. It is no wonder they are losing the expertise from their team."
The commission's report, which explored ethnic and race disparities within education, employment, the criminal justice system and health, argued that the UK is no longer a country "where the system is deliberately rigged against ethnic minorities".
It said the UK "should be regarded as a model for other white-majority countries" although it cannot be considered "a post racial society".
"Too often 'racism' is the catch-all explanation, and can be simply implicitly accepted rather than explicitly examined," the report argued.
"The evidence shows that geography, family influence, socio-economic background, culture and religion have more significant impact on life chances than the existence of racism."
It criticised what it said was the "confusing" way the term "institutional racism" has been applied, arguing it should only be used when there is proven deep-seated, systemic racism present and not as a "catch-all" term for any microaggression.
Addressing calls for the curriculum in British schools to be "decolonised", the commission said "neither the banning of white authors or token expressions of black achievement will help to broaden young minds".
"We have argued against bringing down statues, instead, we want all children to reclaim their British heritage. We want to create a teaching resource that looks at the influence of the UK, particularly during the Empire period."
It added: "There is a new story about the Caribbean experience which speaks to the slave period not only being about profit and suffering but how culturally African people transformed themselves into a re-modelled African/Britain."
Labour shadow justice secretary David Lammy said black Britons were being "gaslighted", while fellow MP Diane Abbott told Sky News the report was "more about politics than the policy" and "taking us back in the argument for racial justice, not taking us forward".
Dr Tony Sewell, the chairman of the commission, said suggestions it was seeking to "downplay the evil of the slave trade" were "absurd".
Dr Sewell faced accusations of putting a "positive spin on slavery and empire" when explaining a recommendation on teaching history in schools in the report's foreword.
"It is absurd to suggest that the commission is trying to downplay the evil of the slave trade. It is both ridiculous and offensive to each and every commissioner," he said in a statement on Thursday.
"The report merely says that, in the face of the inhumanity of slavery, African people preserved their humanity and culture."