The chair of the body overseeing the construction of the National Children’s Hospital has stepped down.

Tom Costello says he has decided on the move to help ensure focus is restored on delivering the project.

The National Children’s Hospital’s been mired in controversy over spiralling costs of the new facility from an original estimate of €650 million.

In a statement, Mr Costello says he is concerned over the reputational damage the controversy is having on the project.

He says he acted with professionalism and integrity in all his dealings with project stakeholders.

Health Minister Simon Harris has accepted his resignation and thanked his for his service and exceptional commitment to the project in the last six years.

Waterford Sinn Féin TD David Cullinane, who is a member of the Public Accounts Committee which has probed the spending on the project, said he hoped the resignation was not designed to give “political cover” to Mr Harris as well as to previous Fine Gael health ministers, including Taoiseach Leo Varadkar.