Britain risks a repeat of riots that buffeted its cities earlier this year unless it does more to help young people who feel they have nothing to lose, the head of the Church of England said on Tuesday.

Britain is debating the causes of its worst riots for three decades, which broke out in August after police shot dead a black suspect in a poor area of north London.

Looting and mob violence spread across the suburbs of the capital and to the major cities of Birmingham and Manchester, leaving five people dead and many shops wrecked or burned, before a mass police deployment restored order.

Writing in the Guardian, Archbishop of Canterbury Rowan Williams said the coalition government, schools and families had to reach out to an alienated youth.

We have to persuade them, simply, that we as government and civil society alike will put some intelligence and skill into giving them the stake they do not have, Williams said.

Without this, we shall face more outbreaks of futile anarchy, in which we shall all be the losers, he added.

Britain is an increasingly secular society but the Church of England retains the largest following of any faith and Williams' words carry weight.

Williams told the Conservative-led coalition to consider the impact of spending cuts on the young, more than a million of whom are out of work and who face sharply higher student tuition fees if they go to university.

The idea that cutting youth services is ever a true economy -- never mind the ethics of it - should be indefensible, he said.

Williams, spiritual leader of the world's 77 million Anglicans, has previously said that the rich are not taking their fair share of the pain from spending cuts and other austerity measures, and backed the anti-capitalist protesters who have set up camp in the shadow of St Paul's Cathedral in the heart of London.

Anger with the police and a desire to get goods they could not afford emerged as the main causes of the riots in a study by the Guardian and the London School of Economics published this week. The study was based on interviews with 270 rioters.

Income inequality rose at a faster rate in Britain than in any other major economy in the past two decades, the OECD said in a report published last week. More than one in five under-24 year olds are unemployed.

(Reporting by Keith Weir; Editing by Tim Pearce)