Image copyright Getty Images Image caption Oliver Letwin is one of David Cameron's longest-serving ministers

David Cameron's policy chief has apologised "unreservedly" over remarks he made about black communities days after the 1985 Broadwater Farm riot in north London.

In a newly-released memo, Oliver Letwin - then adviser to Margaret Thatcher - blamed unrest on "bad moral attitudes".

He also dismissed plans to encourage black entrepreneurs, saying they would set up in the "disco and drug trade".

Mr Letwin said parts of the private memo were "badly worded and wrong".

His statement came amid mounting calls from senior Labour figures for him to apologise.

The party's deputy leader, Tom Watson, said the comments were evidence of "an ignorant and deeply racist view of the world", while MP Chuka Umunna said attitudes in the memo were "disgusting and appalling".

But a government source told the BBC it was a "historical" document "written by a policy team whose main task was to challenge orthodox views".

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The Broadwater Farm riot followed the death of estate resident Cynthia Jarrett, who died of heart failure after four policemen burst into her home during a raid on 5 October 1985. Police said they were looking for stolen property but found none.

Mrs Jarrett's death sparked riots in which more than 230 police officers were injured and PC Keith Blakelock was killed after being stabbed 43 times.

Image copyright PA Image caption A deserted street in Tottenham, north London, following the Broadwater Farm riot

The 1985 memo, written by Mr Letwin and future Conservative MP Hartley Booth, urged Mrs Thatcher to ignore claims that rioting in mainly black inner city areas was caused by social deprivation and racism.

"The root of social malaise is not poor housing, or youth 'alienation', or the lack of a middle class," they wrote in the document, which has been released by the National Archives.

"Lower-class, unemployed white people lived for years in appalling slums without a breakdown of public order on anything like the present scale; in the midst of the depression, people in Brixton went out, leaving their grocery money in a bag at the front door, and expecting to see groceries there when they got back.

"Riots, criminality and social disintegration are caused solely by individual characters and attitudes. So long as bad moral attitudes remain, all efforts to improve the inner cities will founder."

Image copyright PA Image caption Downing Street papers have been released by the National Archive

Image copyright National Archives Image caption The memo was written by Oliver Letwin and future Conservative MP Hartley Booth

The pair, who were members of the Downing Street policy unit, poured scorn on plans put forward by two government ministers to tackle bad housing and encourage new black middle-class entrepreneurs as a "force for stability".

"David Young's new entrepreneurs will set up in the disco and drug trade; Kenneth Baker's refurbished council blocks will decay through vandalism combined with neglect; and people will graduate from temporary training or employment programmes into unemployment or crime," they said.

Image copyright Getty Images Image caption More than 230 police officers were injured and Pc Keith Blakelock was murdered in the Broadwater Farm riot in Tottenham, north London

They argued government should place "young delinquents" in "good" foster homes and create a new "youth corps" to promote "moral values" and encourage "personal responsibility, basic honesty" and respect for the law from an early age.

In a follow-up paper, Mr Booth attacked plans for a £10m communities programme, suggesting it would do little more than "subsidise Rastafarian arts and crafts workshops".

The proposals were strongly criticised at the time by cabinet secretary Sir Robert Armstrong, who warned Mrs Thatcher that the proposed attempts at "social engineering" raised some "very large and problematic questions".

'Disgusting and appalling'

Labour's David Lammy who grew up alongside the Broadwater Farm estate, said the riots "had nothing to do with moral bankruptcy and everything to do with social decay and the appalling relations between black youths and the police".

He said the memo was "an indication of how the powerful can be so utterly, utterly out of touch with what's going on".

Image copyright PA Image caption Cynthia Jarrett died while police officers searched her home in Tottenham

Image copyright Police Image caption PC Keith Blakelock was stabbed 43 times

Mr Umunna, who grew up in Brixton at the time of the riots, said: "The authors of this paper illustrate a complete ignorance of what was going on in our community at that time, as evidenced by their total and utter disregard of the rampant racism in the Met Police which caused the community to boil over - there is no mention of that racism in their paper.

"The attitudes towards the black community exhibited in the paper are disgusting and appalling. The tone of it in places is positively Victorian."

'No offence intended'

Speaking on BBC Radio 4's Today programme, former head of the Equality and Human Rights Commission Trevor Phillips said he did not think Mr Letwin's remarks "would have raised a single eyebrow at the time".

He added: "My guess is that he's a grown-up now, he has met people and he has different views."

Mr Letwin, now the minister for government policy in the Cabinet Office, said: "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."

A Cabinet Office spokesman said: "We remain thoroughly committed to helping the most vulnerable and ensuring that nobody is confined by the circumstances of their birth."

Mr Booth has been approached by the BBC for comment.

Bomb-making fears

In separate papers released by the National Archives, government advisers expressed fear that potential rioters were arming themselves with napalm following the unrest.

Downing Street files also show Mrs Thatcher told then Home Secretary Douglas Hurd the government "should stand up for police" and proposed extra search lights as well as the possibility of demolishing homes in "difficult estates".

The archives also reveal government advisers feared a milk float in north London had been "abducted" to use the bottles to make petrol bombs.