Simon Coveney has been warned his pledge to end the use of hotels as accommodation for homeless families by June cannot be achieved.
Fianna Fáil TD Barry Cowen said the housing department "can't square that circle" in the absence of promised rapid-build housing, much of which won't be delivered until 2018.
Meanwhile, Anti-Austerity Alliance TD Ruth Coppinger questioned if Mr Coveney hoped to resolve the situation this year or next, adding this June "seems like an absolute impossibility".
The June promise was contained in Mr Coveney's 'Rebuilding Ireland' strategy to tackle the housing crisis.
Mr Coveney previously vowed that despite a view that he was "crazy" to pledge an end to homeless families in hotels, he is "going to make that happen".
But concerns about hitting the deadline came as Department of Housing secretary general John McCarthy briefed an Oireachtas committee on progress in the plan.
Mr McCarthy said that in addition to the Housing Assistant Payment (HAP), a "key element" of the plan to end the use of hotels for homeless families is the provision of 1,500 rapid-build homes by the end of 2018.
Mr Cowen seized on figures provided by Mr McCarthy showing there were 4,436 adults in emergency accommodation in November 2016. He asked how many homeless children are in hotels. And with just 2,000 people taken out of homelessness last year, he questioned if thousands of people in hotels could be reduced to zero by June.
He put it to Mr McCarthy that if one of the tools used to achieve this is rapid-build housing that won't be fully delivered until the end of next year, "unfortunately you can't square that circle". He argued just 22 rapid-build homes were completed last year and he accused the department of a "lack of urgency".
Mr McCarthy said there were 2,549 children in emergency accommodation among 1,200 families. He said 700 of these families are in hotels in Dublin.
He clarified that the pledge is to rehouse families living in commercial hotels, not all homeless individuals. But he told Mr Cowen: "You made a valid point in relation to my reference about the whole rapid-build programme being completed by 2018 and how that gels with the mid-year target that we have for hotels."