Geneva  - The sub-prime mortgage crisis has exposed the crisis in governments' housing policies and could still hit the middle classes, the United Nations' expert on urban planning said on Monday.

Sub-prime mortgages, given by lenders to people who could not afford them, are widely blamed for triggering the meltdown in US banks and the global liquidity crisis and economic downturn.

Raquel Rolnik, a Brazilian urban planner appointed to the role of special rapporteur on housing by the Human Rights Council a year ago, said the crisis had revealed the need for governments to reform housing policies.

She said the reduced involvement of the state in housing helped contribute to the need for people to take loans they could not afford, placing both themselves and the lenders at increased risk.

With the downturn, more people will find themselves unable to afford an acceptable place to live, she added.

"It is a blunt reminder that it is not just the poor, but also low-income and - increasingly - middle-income groups, who find it difficult to raise enough money to buy or rent adequate housing," said Rolnik.

She said that as part of dealing with the economic woes, governments should review their housing programmes and policies. (dpa)