The Government could be facing court action against the decision to press ahead with plans for the new National Children's Hospital.
The Connolly for Kids Hospital campaign group and the Jack and Jill Foundation have sought legal advice after the project at the St James' Hospital in Dublin got the green light.
Founder of Jack and Jill, Jonathan Irwin, says the Government has refused to listen to the parents of sick children.
"We've sent the Cabinet, each one of them, an email and a hard copy of a number of letters that we'd like them to answer, and do you know what? A deafening silence," he said.
"Not a reply to any of the questions that are vital to the parents of sick children.
"I find it quite shocking, and I know that the parents of Ireland at the General Election will just trash Fine Gael."