Housing associations Helm and Trinity failed to build homes with public grants
Almost £9 million of public grants to housing associations did not produce any social houses in Northern Ireland, a watchdog said.
The Helm and Trinity organisations received the money.
Helm did not use land at Great Georges Street in Belfast purchased using public money. Trinity failed to build on land in Crossgar, Co Down, due to problems with planning permission, Stormont's Public Accounts Committee said.
Chairwoman Michaela Boyle said: "It seems clear from the evidence given to the committee that prior to then the scheme was wide open to abuse."
Housing associations receive a substantial amount of grant funding from the Department for Social Development (DSD) each year to allow them to develop new social housing in Northern Ireland. Over the last three years DSD has paid grants to housing associations of £308 million and this has been even higher in the past.
The report, entitled Inquiry into DSD Advanced Land Purchases, looked at how the DSD provided money to associations.
Two grants to Helm and Trinity Housing Associations, with a combined value of £8.9 million resulted in no social housing being built, the investigation found.
Ms Boyle said it was deeply worrying.
"We were also extremely concerned that not only did Helm not use land at Great Georges Street purchased by a Department grant of £8.1 million, a third party was able to buy the land at a lower price and then sell it to Helm - netting the third party a profit of £3.25 million within 24 hours.
"This is completely unacceptable and has never been explained, despite being investigated."
A second case, involving Trinity, involved a grant of £800,000 in 2008 to develop housing in Crossgar. No social housing was ever developed, due to problems in gaining planning permission, but when the Department requested that the grant be repaid in 2012, Trinity threatened legal action to retain the funds.
Ms Boyle said: "The committee views Trinity's decision to threaten legal action as unacceptable because the association had a public duty to repay the grant when it had not been possible to progress the development.
"We are also appalled that the agreement to recover the grant, which was only reached in 2015, allowed Trinity to retain £200,000 to cover expenses incurred at the site even though no development had taken place.
"Again no interest has been charged to the association."