By Jennifer Hill

LONDON (Reuters) - Government house-building targets are insufficient to stave off a housing crisis, an independent body says.

The National Housing and Planning Advice Unit said the housing affordability crisis was set to deepen, despite government plans to build 240,000 new homes per year.

It said house prices could soar to up to 11 times average earnings, based on current building activity, from a current level of around seven times typical salaries.

Some 270,000 new homes per year are needed to "stabilise" the ratio of house prices to income, it said.

Professor Stephen Nickell, who helped write the report, told BBC Radio: "Our projections suggest that, if we stick to existing house-building plans, they (house prices) could get up to as much as 11 times incomes.

"If, however, the government succeeds in getting their 240,000 plans a year going, then it would be somewhat less than that, but still as much as nine times average incomes."

The report said that properties in the southeast, southwest and east of England could become more expensive relative to average pay than those in London over the next 20 years.

Nickell said demand for housing across the southeast of England, excluding London, was growing very rapidly.