The broadcaster made the comments after an investigation found “pervasive racism” underpinned a failure to properly commemorate potentially hundreds of thousands of service personnel who died fighting for the British Empire.
The Commonwealth War Graves Commission (CWGC) has apologised after its investigation found that those individuals were not formally remembered in the same way as their white comrades.
The special committee behind the investigation was established in 2019 after a documentary on the issue, titled Unremembered and presented by Labour MP David Lammy.
Professor Olusoga, whose TV company produced the documentary, said the commission must ask itself “urgently” what action they should take. He told BBC Radio 4’s Today programme: “It is an absolute scandal. It is one of the biggest scandals I’ve ever come across as an historian, but the biggest scandal is that this was known years ago.”
He added: “These are men who died fighting for Britain in the most appalling war Britain’s ever faced, the war that killed more British soldiers and more Commonwealth soldiers than any conflict in history.
“It is a war that changed our culture and part of the impact of the First World War was the power of the way those who fell were memorialised.”
Defence Secretary Ben Wallace was due to give a statement to MPs on the findings on Thursday.
The investigation found that at least 116,000 mainly African and Middle Eastern First World War casualties “were not commemorated by name or possibly not commemorated at all”.
The figure could be as high as 350,000, according to the report obtained by the PA news agency.
CWGC director general Claire Horton said: “We recognise the wrongs of the past and are deeply sorry and will be acting immediately to correct them.”