The Social Democrats has criticised Government plans to increase the allowance for cabins or garden homes up to a size of 45 sq.m as a "half-baked plan" to move people into "glorified garden sheds".
The Cabinet heard that a public consultation will begin today on a proposal to increase the allowance for cabins or garden homes up to a size of 45 sq.m.
This is larger than the original suggested upper limit of 40 sq.m.
Under current rules, an extension to the rear of a property is exempt from planning once it is 40 sq.m and is attached to the property.
Under the plan, the units must comply with building regulations while the size of the residual private garden space of 25 sq.m must be retained and set back from boundary walls.
Social Democrats Spokesperson on Housing Rory Hearne said that "there are real concerns about the impact of allowing a huge number of unregistered log cabins proliferate ... without regard for sufficient sewerage facilities, water capacity or fire safety access".
He described the Government plans as "haphazard" and "open to exploitation".
Speaking on RTÉ's Drivetime, Mr Hearne said young people living at home would not have any more independence in a back garden cabin compared to their childhood bedroom.
"If you've terraced house, for example, and a cabin is put out the back of a home, to access that home you have to go through the main house to get to it.
"Questions arise immediately in terms of, for example, fire safety access," Mr Hearne said.
Mr Hearne said that young people need "genuine homes" to live independently.
"I am completely in support of modular housing ... the issue is not the form of construction; the issue is putting it in back gardens with no regulation," he added.
The plan was brought forward to the Cabinet today by Minister of State for Planning John Cummins along with Minister for Housing James Browne.

Mr Cummins said the plan is a practical and common sense move which will provide housing options for people such as those with a disability or young persons who wish to live independently of the family home in the short-term.
Mr Cummins added that the plan will also give the option for parents who wish to 'right-size' within their own community while maintaining the support of their family.
However, Mr Hearne said the proposal will allow for units "larger than the minimum 32 sq.m apartments that will be permitted under proposed changes to existing guidelines".
"While some flexibility is warranted here, there are real concerns about the impact of allowing a huge number of unregistered log cabins proliferate in urban back gardens without regard for sufficient sewerage facilities, water capacity or fire safety access.
He added: "The Government's half-baked plan seems to be to simply move people from their parents’ spare bedrooms into glorified garden sheds.
"Rather than undertaking a radical reset of housing policy, this is an ill-thought-out distraction from the Government’s failures."
Sinn Féin leader Mary Lou McDonald said she understood that some individuals would welcome the proposal to drop the requirement for planning permissions for garden cabins or modular buildings, but she added that the answer to the crisis could not be people "erecting sheds" in their back gardens.
Mr Cummins said that cabins and garden homes will share utilities and bills with the main property rather than being treated separately.
Also speaking on RTÉ's Drivetime, Mr Cummins said people who build these structures will have to notify their local authority and comply with building regulations.
"There is no subdivision of property or plots or properties here. This is, effectively, an extension of the family home, albeit that it is separated from it.
"So, all of the same measures that you would implement if you were putting a domestic extension onto the rear of your dwelling; the exact same measures will apply here," Minister Cummins said.
He added: "What I do envisage, however, is a notification process to local authorities where they will notify them that they are installing a modular unit to the rear of their dwelling and saying that it meets the required guidelines in that respect.
"We do that when we are allowing exemptions for converting former pubs into residential units."
The public consultation on the plan will last for four weeks.
Cabinet agrees further €700m in funding for housing this year
Meanwhile, the Department of Housing received additional funding of nearly €700m this year to fund more social and affordable housing among other measures.
The funding was signed off by the Cabinet this morning.
It brings the overall additional allocation to the Department to over €1.4bn for 2025 and is separate to the €40bn announced as part of the National Development Plan last week.
Some of the additional money will also go to fund second-hand acquisitions and the tenant in situ scheme, as well as to tackle vacancy and dereliction.
A full breakdown of allocations to local authorities will be published next week.

Speaking on his way into Cabinet, Mr Browne said the funding would provide for 4,000 new builds in the coming years, and another 600 from vacancy, dereliction and second-hand acquisitions.
The Cabinet also agreed another housing measure to increase the zoning target for local authorities to 83,000 units per year up to 2034. This is up over 50% on the current target of 55,000.
Mr Browne said that he will be writing to local authorities in the coming weeks to increase the amount of land to be zoned across the country, and that he wanted local authorities to "move quickly" to get the land rezoned.
"They can do that in about 12 to 14 weeks if they really move quickly, and I expect their councillors and people within those local authorities to demand their local authorities move as quickly as possible.
"The reality is that the zoning will have a bigger impact in the coming years than this particular year, but there are other measures.
"They will be there as well to feel like part of a package with all the other measures we're taking," he said.
Ms McDonald accused the Government of a lack of ambition in tackling the housing crisis.
She said it had failed to embrace the call from the Housing Commission for a radical change in addressing the problem.
Reacting to the coalition's housing decisions made at Cabinet today, she said: "The unfortunate thing is the Government has come up blank with any ambitious plans for affordable housing at scale, all they are offering are minimal sidebar issues and I find that very, very alarming."
Electricity supply bill
A new law with the aim of strengthening the resilience of the electricity grid was discussed by the Cabinet.
The bill is a response to the prolonged electricity outages seen after Storm Éowyn earlier this year.
Minister for Energy Darragh O'Brien brought the outline of the Electricity Supply Amendment Bill which will set standards for forestry maintenance and planting.
Storm Éowyn caused extensive and widespread disruption to the electricity network, with damage ranging from broken poles and lines to significant destruction in several areas.
The storm exposed critical vulnerabilities regarding unmanaged vegetation and commercial forestry close to electricity infrastructure.
The bill sets out a statutory regime to safeguard electricity infrastructure when passing through forestry.
It will give additional vegetation management powers to ESB Networks, and the attachment of maintenance responsibilities to landowners with a compensation mechanism to their interests.
Infrastructure report
Minister for Public Expenditure Jack Chambers brought a report by the department's infrastructure division outlining barriers delaying the delivery of infrastructure following consultation and engagement.
These include the increased regulatory and legal burden for those developing key infrastructure, inconsistent planning decisions, and limits on regulatory agencies’ ability to prioritise and consider wider societal aims and limited public awareness of the consequences of poor infrastructure.
The report places a heavy emphasis on the impact of judicial reviews and the growing threat of judicial reviews on the delivery of key infrastructure.
It is estimated that the planning and consenting process for critical infrastructure takes three to five years longer due to the added threat, duration and impact of judicial reviews.