Construction company BAM has been invited before an Oireachtas Committee to answer questions on the new National Children's Hospital.
The Secretary General for the Department of Public Expenditure is also due to appear before the Public Accounts Committee.
It comes as politicians attempt to establish the cause of massive overruns at the hospital.
Sinn Féin's Louise O'Reilly says the government should be giving more thought to re-tendering for the project.
"The retender offered by Bam was issued and I think it was 20 hours later the Minister for Health had dismissed that out of hand.
"But I'm wondering what consideration has been given.
I'm also wondering the terms of reference for PWC with regard to this project, do those terms of reference encompass examination of different options even at this late stage.
Meanwhile, a Fianna Fáil TD has said "medical elitism" was at play in choosing the site for the new National Children's Hospital.
Some campaigners argue the location at St James' in Dublin is too congested and is difficult to get to.
Former Health Minister James Reilly has defended the decision to put it there, saying it was led by the best advice and is co-located with a major hospital.
However, Fianna Fáil TD Marc MacSharry has suggested doctors played a part by not wanting to live in areas further out where there could have been a greenfield site.
Mr MacSharry said: "I'm not sure just why we ended up where we ended up.
"I do sense that a lack of leadership politically and also the fact that there is medical elitism too, that there are people who prefer to be in certain locations, or feel that they should be in certain locations."