Rates of home completions are far below what is needed to reach targets set just last year, the Scottish Labour Party said.
And it claimed the targets were already too low to deal with a housing crisis that has driven 21,000 people to ask charities for help dealing with homelessness or avoiding becoming homeless in the past year.
In 2016, Scottish ministers pledged £3 billion to build 50,000 affordable homes, 35,000 of which are destined for the social rented sector.
However, the number of affordable homes completed per quarter since the middle of last year has averaged at just 1,808, well below the 2,673 needed to reach the 50,000 target by 2021. The gap in completions for social rent is even wider, with an increase in the completion rate of 159% needed to meet the target.
Labour’s housing spokeswoman Pauline McNeill MSP said the government’s targets themselves did not meet the call from housing charity Shelter to build 60,000 affordable homes by the end of the parliament.
“The SNP has turned a housing shortage in Scotland into a housing crisis and we can see from these figures that they are not even beginning to solve the problem,” she said.
“Nicola Sturgeon’s government is well short of where it needs to be to meet its house building target by the end of the Parliament, requiring a colossal 159 per cent increase in the number of homes for social rent constructed per financial quarter.”
Ms McNeill added: “The SNP must listen to Labour and deliver a radical house building strategy that gets to grip with the chronic housing shortage in Scotland.”
Housing Minister Kevin Stewart said Scotland was building more affordable homes per head than England and Wales. Mr Stewart said: “Since 2007 we have delivered over 69,500 affordable homes, and our previous target was exceeded by more than 10%.
“Through the More Homes Scotland approach we are markedly increasing housing supply, and every council will share £422 million to deliver more affordable homes in their communities.
“Our recent rental Income Guarantee Scheme will boost the emerging build-to-rent sector, we’ve ended right to buy in Scotland, and reintroduced council house building. All of that is supporting our commitment to deliver 50,000 affordable homes during this Parliament.”