A demonstration is being staged in Dublin today to highlight the plight of homeowners whose houses have been structurally damaged because pyrite was used in their construction.

The mineral can expand over time, leading to problems which cost thousands of euro to put right.

Around 50,000 homes in Dublin, Meath, Kildare and Offaly are thought to be affected, and more cases may yet show up.

Homeowners say Homebond guaranteed them cover against such damage and that the firm is now "burying its head" over the issue as it under-insured many properties.

Councillor Ruth Coppinger of the Socialist party said the Government had to intervene to protect cash-strapped homeowners.

"The Government oversaw the under-insuring of these homes, and will have to deal with this problem…people invested and bought homes in good faith," she said.