The cost of the mica redress scheme has cost the exchequer more than a billion euro already, the Housing Minister said.

Defective building blocks containing the mineral mica have caused cracks and fissures to open up in an estimated 5,000 to 6,000 homes primarily in Donegal and Mayo.

A Government redress scheme, established in January 2020 before the last election, has offered 90% of renovation costs to those affected.

Campaign groups say this is insufficient and are calling for 100%.

Housing Minster Darragh O’Brien briefed Cabinet colleagues on Wednesday, but no formal decision was made.

He said he wants to work with those affected but warned the cost to the taxpayer will be substantial.

“The scheme itself isn’t insignificant. I do want to say this to you, if you’re looking at it from an exchequer perspective, the potential cost to the exchequer here is over a billion euro already,” he told Today FM’s The Last Word.

“You’re looking at a liability to the exchequer of about a billion euro, of a maximum cost per home of 275,000.

“That is very significant that I think listeners will understand that too, but these are people’s homes. We want to help where we can.”

Mr O’Brien said the costs involved far outstrip those of the pyrite scandal, which emerged in 2014 and also involved faulty materials resulting in damage to homes.

“There was a much smaller cost there of 65,000 euro per unit and the total cost to the exchequer so far has been about 160 million in total. So it is very different,” he said.

Mr O’Brien has acknowledged that the mica scandal may extend beyond family homes, and could have impacted some community buildings such as schools and hospitals.

Sinn Fein leader Mary Lou McDonald backed campaigners’ calls for 100% redress following a visit to Donegal last week.

She said: “The mica scandal in Donegal has devastated families whose homes are literally crumbling around them.

“These are families who have worked hard and saved hard to buy a home. Now, through no fault of their own, they find themselves in a nightmare situation where their houses are cracking and coming asunder around them.

“The scheme that the Government put in place is not working. Under this scheme, some families are expected to come up with 100,000 euro or more to contribute to fixing their homes.

“This is incredibly unfair. These families have been failed by the system.

“The only fair solution is for the Government to deliver a 100% redress scheme and deliver it urgently.”

Earlier on Wednesday, Tanaiste Leo Varadkar said the Government is examining the options available.

He said: “We do appreciate this is a real difficulty for people in Donegal and other counties. We are keen find a solution.

“We understand what people are saying in terms of the disparity between the pyrite scheme and the mica scheme.

“The pyrite scheme, which was 100% and provided for rent, for example – this one doesn’t provide for either.

“We are examining that so that’s it’s fair and equal.

“We would bear in mind as well that the average cost of fixing pyrite repairs is 65,000 euro and the average cost of fixing (mica) is more than that.

“Also, the whole idea of the scheme is to allow some to replace their house with a house of about 2,000 square metres.

“It would appear some houses are much larger than that and we have to ask ourselves, is it reasonable to ask the taxpayer to fund the reconstruction of quite large houses in some cases.”