SNP Health Secretary Jeane Freeman has refused to guarantee that a new £150 million hospital for sick children in Edinburgh will be open by the end of next year, fuelling concerns about the troubled project.

Freeman said it would not be fair to staff or patients to speculate before the reviews she has ordered have been completed.

She also declined to back NHS Lothian chief executive Tim Davison, who leads the embattled board behind the new build.

NHS Lothian is under the spotlight after Freeman postponed the opening of the new hospital last month.

She overruled the board at the last minute and made the decision amid concerns about ventilation and drainage.

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In a pointed statement at the time, she said: “While this issue has been caught by the final safety checks, I am disappointed and deeply concerned that this was not identified earlier.”

The new "Sick Kids" hospital has been marked by disputes between the board and Integrated Health Solutions Lothian, the consortium responsible for designing, building, financing and maintaining the hospital. Freeman also announced last month that various probes would be undertaken on governance and what went wrong.

However, although these internal NHS reviews are expected to be completed by September, Freeman has not given any indication of an opening date for the hospital.

Asked by The Herald on Sunday whether she could give a guarantee that the hospital will be open in either 2019 or 2020, she said: “It wouldn’t be fair to the staff or patients affected by this delay for me, or anyone else, to give guarantees before we have the facts from the reviews I ordered in July. Anything at this stage is purely speculation.

“That timetable of work I set out last month, when issues with the ventilation in critical care came to light, is on track. Work by Health Protection Scotland and Health Facilities Scotland is well under way and will give me the information I need to base any future decision about a timetable for the move to the new site.”

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On whether she believes that NHS Lothian did not provide her with accurate information about the hospital’s ventilation and drainage at a sufficiently early stage, she said: “I’ve asked KPMG, who are also now on site, to independently review the governance arrangements for the new children’s hospital to establish the factors that led to the delay.”

Asked directly if she has confidence in Davison’s abilities to continue as CEO in the long term, she did not offer him her support: “We know that the entire senior leadership team in Lothian is working hard to resolve these matters. We will continue to work with the team to provide support where appropriate and to ensure that they have the capacity they need to both deliver continued standards of high-quality patient care and plan for the safe transfer of services to the new site.”

Labour MSP Monica Lennon said: “It is worrying that she has no idea if the hospital will be declared safe to open next year in 2020 – this is astonishing and shows how badly this project has been managed. Every single day that this hospital lies empty is wasting money that could be benefiting patients. It’s a disgrace and Scottish Labour demands an independent public inquiry.”

In an interview with The Herald on Sunday last week, trade union official Tam Waterson, who represents staff at NHS Lothian, claimed that drainage is a bigger issue than the ventilation concerns.

He warned: “We know the drainage is not fit for purpose. It’s been flooded twice with nobody in it. There is a school of thought that they might have to rip it down [the building].”

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Freeman responded and said: “There are no plans to pull down the building and there is no evidence to support this claim. As I have already said, if there is evidence to support such an assertion, then it should be brought to the Scottish Government.”

It also emerged last week that NHS Lothian is paying around £1.4m a month to use the building, even though it is not operational.

Tory MSP Miles Briggs said: “SNP ministers and NHS Lothian are both equally responsible for this unimaginable fiasco and have completely failed to explain how these problems are going to be fixed.

“Jeane Freeman increasingly looks like a rabbit caught in the headlights, unable to provide even the most basic information to families and NHS staff on the potential opening date for the new Sick Kids.”