David Cameron’s Hampstead-born policy chief Oliver Letwin has apologised “unreservedly” for remarks he made about black communities in the wake of the 1985 Broadwater Farm riots in Tottenham.

The Conservative MP blamed “bad moral attitudes” for the unrest in a memo to Margaret Thatcher in his role as an adviser in the former prime minister’s No 10 policy unit.

The files released yesterday (Wednesday) by the National Archives show that Mr Letwin poured scorn on claims that the riots were the result of urban deprivation, saying that white communities had endured poverty for decades without disturbances.

He also dismissed proposals by ministers to promote a new class of black entrepreneurs, saying they would simply set up in the “disco and drug trade”.

The Cabinet Office minister – who ran unsuccessfully against Labour’s Glenda Jackson in Hampstead and Highgate in 1992 – yesterday said in a statement: “I want to make clear that some parts of a private memo I wrote nearly 30 years ago were both badly worded and wrong.

“I apologise unreservedly for any offence these comments have caused and wish to make clear that none was intended.”

His remarks were strongly condemned by Labour polticians yesterday, including Tottenham MP David Lammy.

Mr Lammy, who grew up near the Broadwater Farm estate, said: “It had nothing to do with moral bankruptcy and everything to do with social decay and the appalling relations between black youths and the police.

“Mr Letwin’s statement is an indication of how the powerful can be so utterly, utterly out of touch with what’s going on.”

Deputy Labour leader Tom Watson MP said Mr Letwin’s comments were evidence “of an ignorant and deeply racist view of the world”.

The riots across Britain in autumn 1985 were among the worst in recent times. The Broadwater Farm riot saw Pc Keith Blakelock stabbed to death, and was sparked by the death of Cynthia Jarrett, who died after four police officers raided her home.

Police said they were searching for stolen property but found none.