House-builders have defended their industry against accusations of opportunism during a period of flux in the planning system.

Steve Turner, head of communications for the Home Builders Federation, said: 'Like many areas, South Norfolk is experiencing an acute housing shortage, whilst house prices have rocketed from an average �80,000 in 2000 to more than �180,000.

'This has priced many potential first time buyers out of the market, resulting in many young people having to stay with their parents or rent with friends and delay starting their own families.

'In fairness, South Norfolk, along with Broadland and Norwich City Council, has recognised the housing needs of its communities and set a realistic house building target.

'However, what local people and house builders now desperately need is certainty as to where these homes are to be built and the local authority urgently needs to set out its 'five year land supply' – a requirement since 2007.

'Most people accept that homes have to be built. Local authorities need to provide leadership and meet their responsibilities. Detailing exactly where it proposes to build the homes it says are needed will allow developers to work with local communities to deliver the type of housing their areas need.'

A report released yesterday by the Federation of Master Builders (FMB) underlines the need for new homes, saying demand will outstrip supply by more than half a million units by 2015 – equivalent to a city the size of Birmingham.

Roly Beazley, chairman of Country Land and Business Association (CLA) Norfolk and head of the rural department at Savills estate agents in Norwich, said landowners should not be criticised for weighing up their options.

'It has become particularly tricky in the last few months, but we didn't set the rules,' he said. 'If you are a landowner, you dip your toe in the water because the consultation asks you to. Ultimately it is for the planning system to decide what happens. Most landowners take a very long-term view on taking farmland into alternative use, and they want to see a balanced development that meets the community's long-term needs.'

?Browse our 'Urban Sprawl or Vital Growth' section for stories on the growth plans of the GNDP (Greater Norwich Development Partnership).