Deep-seated official prejudice against black people led to unrest in the 1980s Graham Turner/Getty Images

A senior policy adviser to Margaret Thatcher claimed that cannabis use was so rampant within the black community that they gave the drug to babies, a newly released archive file has revealed.

Carolyn Sinclair, who later led a government unit responsible for promoting racial equality, said that the drug was “part of life” for black people.

Crack cocaine addiction was also likely to take hold in the community, she wrote in a memo on July 31, 1989, which has just been released by the National Archives in Kew.

At the time, the government was outlining policy to stop a so-called crack epidemic, which was felt to be on the rise in the US, predominantly in African-American neighbourhoods.

“Afro-Caribbeans rarely take ‘hard’ drugs such as heroin,…