Western democracies will only survive if middle class parents are able to see a better future for their children, says former Chief Economist of the World bank Lawrence Summers.

The former US Treasury Secretary who has served under Presidents Clinton and Obama, told an audience at the JW3 centre in north-west London on Tuesday that slow growth and rising inequality will be the most important challenges in the coming decades.

He also said the rate of technological advances will damage wage and employment prospects.

He said: "Countries where parents can confidently look forward to their children living better lives than they have are success stories.

"Conversely, where that objective is not being achieved, it is rare for other objectives to be achieved either, and faith in a system of government, even when it is democratic, diminishes."

He warned that governments must adapt to higher levels of unemployment and people being unable to fund their lives.

"Workers in India can do your job for a fifth of what you expect, and robots are doing what people used to do in manufacturing," he said.

Mr Summers, who recently co-chaired an 18-month commission with Shadow Chancellor Ed Balls on bringing prosperity to the lower and middle classes, said the proliferation of non-human workers would also affect the service sector.

"Automated psychiatry programmes exist, and there is clear evidence to show they work. This kind of technological replacement is also a threat to wages and employment, not to their creators, but for most of our fellow citizens."