The children's ward at Rotorua Hospital will be missing a third of its beds as winter hits because Te Whatu Ora halted an upgrade partway through to review costs.

Doctors and nurses are worried about how they will care for children with the unit not fully up and running until August - well into the peak period for winter illnesses.

Demolition of the old ward had already been carried out when the order to down tools was made in February.

Children were moved to a temporary ward with 14 beds instead of the usual 22.

Work has resumed, but the six-week halt means the new ward would not open until August, deep into the winter peak when most hospitals are beyond capacity.

Doctors and nurses say at times, the temporary space is already overflowing, and some children are being cared for in adult wards.

Clinical staff don't want to speak out publicly but the Association of Salaried Medical Specialists says the issue has come up at a meeting between them and hospital management.

Its executive director Sarah Dalton says clinicians have been blindsided by the decision to stop work.

"They were incredibly shocked. They had had no warning this might happen and of course their natural concern was for the finish date - what does this mean for our ability to provide care for patients?"

Doctors' concerns include:

• children might have to be discharged when they ought to be kept in hospital
• children might not get the same level of nursing oversight if they were in an adult ward
• some children's surgery could be delayed because there was no space for post-operative care

Rotorua Hospital confirmed the construction was stopped so that a "detailed analysis of the future costs of the project" could be carried out.

The health agency has been on a cost-saving drive, with districts told to find $105 million in savings by the end of the financial year.

RNZ understands it was only after protests from Rotorua Hospital staff and management that work started again, in April.

Staff have already been concerned about the original completion date of 1 July - just as winter illnesses ramp up - but by the new date - mid-August - the hospital would have been busy for weeks.

Dalton says project costs have increased, which is not unusual, but she's shocked by the decision to halt for the review.

"It would be different if the build hadn't started and they still had the existing facilities ... but they've really been left high and dry with this approach," she says.

Te Whatu Ora's director of operations for the Lakes area Alan Wilson says if there are not enough beds in the children's ward during the winter peak, "suitable" children over 12 with orthopaedic, ear nose and throat or general surgical care would be cared for in adult wards.

"There will also be a lower threshold for young children who are very unwell to be cared for in Rotorua Hospital High Dependency Unit."

-RNZ.