MORE house building in south Hampshire could increase the risk of flooding and create intense pressure to concrete over Green Belt land, a Government-commissioned report has warned today.

The report by planning experts highlighted a set of risks if building in the crowded South East is increased beyond the current planned rate of 29,000 units a year.

Hampshire is expected to build 6,100 of the new homes a year over the next two decades including 815 annually in Southampton, 207 in the New Forest, 186 in Fareham, 354 in Eastleigh and 446 in Test Valley.

The report by Roger Tym & Partners, obtained by the Conservatives, warns that additional house-building has ''the potential to increase the risk of flash flooding'' and will have ''a negative effect... on the objective to reduce the risk of flooding'' in areas like south Hampshire.

It also said that increasing housing targets would require ''more space for development and therefore will need to use a greater amount of greenfield land''.

Building could have ''a negative effect on the character of the countryside'', as well as driving up road congestion, train over-crowding and water shortages.

The Prime Minister has set out his ambition for 3 million new homes by 2020 - 250,000 more than the previous target.

Many are expected to be built in the South East, where prices have rocketed in recent years, in part due to the shortage of homes to house workers drawn to London's booming economy.