Around £8m earmarked for new social housing has been diverted instead to co-ownership homes aimed at first-time buyers, it has been confirmed.
Both unionist and nationalist Assembly Members have condemned the switch which will allow for 140 homes under the co-ownership scheme.
Ulster Unionist Michael Copeland called it was a "huge indictment" of Social Development Minister Nelson McCausland.
And the SDLP's Mark H Durkan said the decision was "completely unacceptable" and made a mockery of housing being allocated on the basis of need.
But Mr McCausland's department said the co-ownership homes fell within the Stormont Executive's aim of providing "affordable" housing as part of the Programme for Government.
Foyle MLA Mr Durkan said: "There are thousands of people who are on housing waiting lists who will never be able to afford to become first-time buyers.
"It is completely unacceptable that money meant to be spent on building much-needed social homes should be just handed over to something else in this way."
East Belfast MLA Mr Copeland added: "I believe it is a huge indictment on the performance of the Social Development Minister and his department that there was an £8m underspend."