Sinn Féin is claiming serious and substantial works are needed at the National Children's Hospital which could cost millions.
Works are needed to move ceiling grilles in the 11 operating theatres.
Health Minister Stephen Donnelly has denied these are major changes.
"What we're talking about is potential changes that haven't yet been asked for to 11 of 5,000 rooms," he said.
"Discussions like this happen all the time.
"So I think we just need to maintain a sense of perspective as to what we're talking about.
"What frustrates me, which is a substantive issue, is that we don't yet have a compliant programme of works from the contractor," Minister Donnelly added.
Sinn Féin Health Spokesperson David Cullinane told The Pat Kenny Show he finds the Minister's statement 'extraordinary'.
"They keep burying their heads in the sand here when it comes to the National Children's Hospital," he said.
"This is a hospital which is now the most expensive in the world.
"We've had crisis after crisis, cost overrun after cost overrun. We've had a hands-off approach from this Government for far too long.
"Now we have a situation where, this isn't just 11 ordinary rooms - these are very specialist operating theatres.
"One of the key centrepieces of the new National Children's Hospital is that we'll have 22 operating theatres, a doubling of existing capacity.
"The hospital can't function without those operating theatres".
'Substantial additional time'
Deputy Cullinane said he has been told these are major works.
"The information I've been given, and it is from a source that's directly involved in this project... they are very clear that this will cost very significant money," he said.
"It will take about 12 months to remediate the works in their view.
"It may not delay the hospital by 12 months... but it will still add - if this is correct - substantial additional time on to the completion date.
"It's the ceilings which carry gas pipes, oxygen pipes, a live sprinkler system and electricity pipes.
"When you go to dismantle something like this, it isn't just the operating theatre rooms: you have to go right down into the corridors and into the source.
"What is the case, and what is factual which I put into the public domain, was that a change order was given to BAM at the end of May to stop all works on these theatres.
"There was a following change order issued in June to set up workshops with other contractors that are mechanical and electrical contractors... to look at how to resolve this".
Deputy Cullinane said he will publish documents later to 'clearly set out' the delays.
"This is not a snagging problem, this is a major generic fault that requires very substantial work," he added.
'Not on the critical path'
A statement from the the National Paediatric Hospital Development Board has denied these are serious setbacks.
"The potential works in the 11 operating theatres are minor works - they are not on the critical path," it said.
"The change, if instructed to BAM, will involve the movement of four ceiling grilles in each of the 11 theatres. This is not expected to have an impact on the completion date of the hospital.
"There are 5,000 rooms to be completed within the hospital. BAM is being asked to progress works in all areas as quickly as possible - including in the operating theatres.
"Critical issue of concern is that BAM has still not provided a programme of works. This is now months late and as a result BAM is in breach of contract," the statement added.
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