Opponents of the proposed new national children's hospital are prepared to launch a legal challenge to any decision by An Bord Pleanála to "greenlight" the project on the Mater hospital site.

In a move that could delay building work on the new hospital until a new government and health minister take office, Dr Róisín Healy of the New Children's Hospital Alliance confirmed that it will take "whatever options are open to us" to obtain a review of the government's decision.

Fine Gael health spokesman James Reilly TD has pledged to review the project if his party gets into power, while his Labour counterpart Jan O'Sullivan has called for "an independent and honest reappraisal" of the current plans.

Under an amendment to the planning and development acts enacted by government last July, healthcare projects of strategic and national importance – such as the national children's hospital – can be submitted directly to An Bord Pleanála rather than first being submitted to the local authority.

Healy, a member of the faculty of paediatrics at the Royal College of Physicians of Ireland, said the group hopes An Bord Pleanála will rule against the Mater proposals once the case against them has been presented.

"If, in the worst-case scenario, An Bord Pleanála approved it, we would take whatever options are open to us, including judicial review and on to Europe if necessary. We would be doing this because we believe this is critical to the future of the children of Ireland," she said.

"We don't have any particular site in mind. But what we do want is a review of this decision. I wouldn't be confident that Minister Harney is for turning on this. But we have all of the opposition parties who have consistently said they want a review of the decision. So we would be absolutely confident that it would be reviewed under a new government, and by somebody we trust. We do not trust an internal committee of the Department of Health and Children."