Sinn Féin leader Mary Lou McDonald has accused the Government of a "scattered and directionless approach" to delivering housing, in which the Coalition is "talking about everything but delivering nothing."
Speaking during Leaders' Questions in the Dáil, she said the Coalition's "centre piece" is to "build cabins in the back gardens" which proved just how "failed your approach is."
The plan is being looked at as part of Government efforts to tackle the housing crisis. The move would see planning rules on cabins and modular homes in back gardens relaxed.
Extensions of up to 40sq/m to a home can be built without planning permission but approval must be sought if structures of the same size are not attached to the home itself.
Planning exemptions could be introduced for free-standing modular or cabin-style homes.
Ms McDonald said the Government was stating that all options are on the table when it comes to housing delivery, but she claimed the truth was that it "does not have a clue about what to do".
In reply, Taoiseach Micheál Martin repeated that housing is the number one priority for the Government and only this week approved €450m in additional funding for social, affordable and cost-rental housing.
He claimed the Government "are hitting the ground running" while Sinn Féin had opposed significant measures introduced to assist first-time buyers like the First Home Scheme, which enabled 3,000 homes to be purchased.

'Try a cabin out the back'
Earlier, the Social Democrats accused the Government of asking those caught in the housing crisis to "try a cabin out the back".
Social Democrats Housing Spokesperson Rory Hearne dismissed the notion of providing "sheds out the back for a locked-out generation".
Speaking during a Private Members' Motion on the housing crisis, he told the Dáil that the Government is demonstrating "a lack of openness to new ideas, a lack of seriousness", and criticised the absence of the Minister for Housing at the debate.
"There are half a million adults stuck living in their childhood box room, infantilised, lacking hope of starting their own independent life," he said.
Deputy Hearne said official figures ignore those caught in "hidden homelessness", and claimed that the Government's housing policies "are causing a mental health crisis".
He dismissed Government claims "that rents rising further will incentivise the supply of expensive rental properties, that will lead, at some point in the future, to rent falling".
The evidence does not support this claim, he insisted.
Speaking for the Government, Minister of State at the Department of Finance Robert Troy said he was opposing the motion as he claimed it would not deliver on the shared goals of "improving conditions for renters, increasing the affordability of homes and, most importantly, increasing overall supply".
He rejected the suggestion that the Minister for Housing's absence indicated that he is "disinterested".
"I am here representing the Government, and I can assure you that the Minister for Housing is aware of the debate that's ongoing today."
He said the Social Democrats do not accept the Government's view "that the State alone cannot act in achieving this, and that is why we're opposing this motion".
Minister of State for Local Government and Planning John Cummins said he does not see the potential new regulations as a rental measure.
"I see it as the ability of people to be able to have that intergenerational movement within their own community and for younger people to live independently," he said, adding that a public consultation will have to be carried out.
Mr Cummins said this was not a solution to solving the housing crisis but an option for people where suitable.
"This allows for a 40sq/m extension to no longer be attached, but to be detached from the dwelling. I'm not saying that this is a panacea, that it's the solution to the housing crisis," he said.
"I'm saying that this is a potential option that will suit certain circumstances."
More provisions needed to help 'new Irish' seeking to learn Irish language, says Gogarty
Independent TD Paul Gogarty asked the Taoiseach about provisions being made to cater for the "new Irish" who want to learn the Irish language.
Speaking in Irish, the TD said ESRI research showed there is a demand for Gaelscoilenna beyond the current provision, and many parents, who he referred to as "Éireannaigh nua" (new Irish), want their children to learn Irish.
He also said we should speak more Irish in general and said that people often have more French leaving school even though they get eight years more of education in Irish.
Responding in Irish, the Taoiseach said there are more Irish speakers now than before and that Gaelscoileanna had a role in that.
He said there are more Irish speaking elected representatives too and said there is a duty on ordinary national schools to foster the Irish language.
He said every effort should be made to make Irish accessible to new Irish so they get a chance to speak the language as it appears many wish to do.
He said more must be done to support Gaelscoileanna and non Gaelscoileanna.
Additional reporting: Joe Mag Raollaigh