The Windrush scandal has its origins in 30 years of racist immigration legislation aimed at reducing Britain’s non-white population, according to a leaked government report.

This stark conclusion was laid out in a paper commissioned by the Ministry of the Interior that officials have repeatedly tried to invalidate over the past year.

The 52-page analysis by an unnamed historian, seen by the Guardian, describes how the British Empire “relied on racist ideology to function” and how this affected laws passed in the post-war era.

It concludes that the origins of the “inherent racism of the Windrush scandal” lie in the fact that “from 1950 to 1981 every part of immigration or citizenship law aimed, at least in part, at increasing the number of black or brown people who were allowed to live and work in the UK “.

The scandal was found to be due to the failure to recognize that changes in UK immigration law over the past 70 years have had a more negative impact on blacks than on other racial and ethnic groups.

“As a result, the experiences of black communities in the UK home office, law and life in the UK are fundamentally different from those of white communities,” the report said. “The Great Immigration Acts of 1962, 1968 and 1971 were intended to reduce the proportion of non-whites living in the United Kingdom.”

It was not clear why officials were reluctant to publish the document. MP Diane Abbott, who has unsuccessfully tried to get approval from the Special Committee on Home Affairs, said the Home Office “seems unwilling to acknowledge the racism that has tainted British immigration policy for decades”.

The report was commissioned by the Home Office as part of a commitment to educate officials about the causes of the Windrush scandal, which saw thousands of people misclassified by the department as illegal immigrants. After the scandal, ministers agreed to brief all 35,000 Home Office staff on British colonial and black British history.

The report, titled “Historical Roots of the Windrush Scandal,” focuses on immigration legislation in the 20th century rather than recent events, such as the impact of Theresa May’s hostile environmental policies when she was Home Secretary.

The unnamed Home Office historian wrote: “The British Empire relied on racist ideologies to function, which in turn produced laws intended to separate racial and ethnic groups…From the beginning there was concern about Commonwealth immigration of skin color.” In the 1950s, British officials “shared the basic assumption that ‘immigrants of colour, as they were called, were not in the best interest of British society’,” the report states.

The document summarizes decades of “dysfunctional relations between British institutions and black and ethnic minorities” and concludes: “British border policy, which has been run by the Home Office for more than a century, is now closely linked to race and ethnicity in Britain’s colonial history.”

Wendy Williams, an independent inspector who advises the Home Office on changes to be made after Windrush, said in March she was “disappointed” that the report had not been released a year after officials signed it on. It was made available to employees internally, but requests to post were repeatedly denied.

A request for information about the document was rejected. Recognizing that the issue was “a matter of legitimate public interest” and that “openness and transparency” were important, the proposal was nonetheless rejected on the grounds that the Home Office’s response to the Windrush scandal raised “sensitive issues relating to…policy development”. . Publication of the document could “hamper discussions and the ability of ministers to seek free and open advice”.

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Immigration historians have said it is strange to suppress a taxpayer-financed history. There has been speculation about whether the report was withheld internally for a year because its conclusions conflict with the government’s portrayal of race. Last year, the Tony Sewell Commission’s Report on Race and Ethnic Disparities on Race said there was no evidence Britain was a racially institutionalized place. Last month, the prime minister told Parliament: “For centuries, Britain has had a proud history of welcoming people from abroad.”

Simon Woolley, the former CEO of Operation Black Vote and Head of Racial Inequality 10 in July 2020, said the refusal to release the report was “shameful.” “The government is bent on denying the systemic nature of racial inequality, and in this climate historical facts have become inconvenient facts to conceal,” he said.

The report also cites a letter from West Indies Premier Sir Grantley Adams to Conservative Prime Minister Harold Macmillan. Sir Grantley protested that “Britain began to take steps indistinguishable in kind from the foundation of apartheid in South Africa” ​​by introducing the Commonwealth Immigrants Act 1962.

Juanita Cox, a research fellow at the Commonwealth Studies Institute who is working on a research project on the Windrush scandal said: “If they recognized that Home Office legislation prior to 1981 was institutionally racist, it could be that current legislation has also been scrutinized and found to be worse racist. It conflicts with the British immigration system. Just as with the proud image he conveys of welcoming immigrants.”

Immigration attorney Grace Brown, who has worked on behalf of a number of Windrush victims, said the ramifications of the legislation were still being felt. “There is no justifiable reason not to address and correct the persistent and long-term effects of historically discriminatory laws and policies on individuals,” she said.

An Interior Ministry spokesman said the ministry would not name the historian who wrote the story, adding that the Interior Ministry was making progress “to become a more sympathetic and open organisation.”