Housing Associations say many privately built homes are poor quality
Thousands of developers' surplus new build homes in England are being rejected by housing associations as they are not of a high enough standard.
It is estimated there could be as many as 100,000 unsold new-build homes in the UK.
With about 4.5m people on housing waiting lists, the government has set up the Clearing House Fund to help housing associations in England buy some of the surplus housing stock that private developers fail to sell.
Associations across England have already used the fund to buy about 5,000 homes and have funding to buy the same again.
Gavin Smart, of the National Housing Federation said: "It's very hard to put a number on homes we are rejecting.
"But it would be a significant proportion because private developers simply do not have to build to the same standards as housing associations.
"Many of the homes that we are being offered would not meet those standards and quite sensibly housing associations looking at those homes are saying they are not of a suitable quality for them to purchase."
Independent building inspector Steve Nancarrow told the BBC he had found 90 flaws in just one new-build flat valued at £210,000.
Faulty electrics, no hot water, and leaking windows are just some of the problems he discovered.
"It's my job every day to go around people's houses and look at the quality of the units, and it's getting worse and worse.
"They are fobbing them off with rubbish," he said.
In order to be accepted by housing associations, developments have to meet high environmental standards, as well as being built to high specifications and to a minimum size.
In the private sector the specifications are lower and there is no minimum size.
The UK builds the smallest homes in the developed world.
In Holland the average size of a new build dwelling is 115 sq m and in Japan it is 92.5 sq m, while in the UK it is just 76 sq m.
Private developers say there is nothing wrong with their properties, pointing out they are built for a different market and that private homes do not yet have to meet the same standards as those built for social housing.
John Stewart of the Home Builders Federation said: "There is no evidence at all that quality is poor.
"Customer survey results suggest there are very high levels of satisfaction with homes people have bought.
"Space and affordability go together - house builders have to build what house buyers can afford to buy."
Both the Royal Institute of British Architects and the Chartered Institute of Housing believe the government should force all builds to have higher minimum standards.
Richard Capie from the Chartered Institute of Housing said: "We have got to say to ourselves the homes we are building today will be here for generations.
"If we make them too small or if we don't for instance have enough storage and they are not going to meet the needs of families and individuals, then we are going to pay the price for that later on."
A Communities and Local Government spokesman said: "The government is committed to very high standards for all homes, whether privately or publicly funded, and we have been improving standards continuously.
"For instance we have made all new homes 40% more energy efficient since 2002, which saves people money on their energy bills and cuts carbon emissions.
"Any new development also has to go through the planning process, whereby local authorities ensure that only proposals with good design, layout and density can be built."