He said when Ms Freeman announced that the move to the new hospital was being halted at the last minute, she wrongly claimed she was overruling NHS Lothian when in fact the health board had not made any recommendation on whether the move should go ahead or not.

In an outspoken interview, Mr Houston, who quit in January over “fundamental and irreconcilable” differences with the SNP minister, also criticised her for denying that the NHS was in crisis and described how she said she would sack him if he did not resign.

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Recalling the day last summer when the Sick Kids crisis broke, Mr Houston said: “When we got the word from our independent testers there was potentially a show-stopping problem with the ventilation systems in critical care, it was like a bomb going off. It was devastating.

“I remember Tim Davison [NHS Lothian chief executive] walking into my office, white as a sheet, and the two of us just couldn’t believe this was happening. The whole place was just knocked sideways by it.”

But he said an emergency meeting of the project team, the NHS Lothian executive team and their advisers had quickly identified where issues could have arisen.

Another meeting had drawn up options over what to do about the new building – go ahead with the move, halt everything or go ahead with some kind of partial move.

Mr Houston said: “That meeting of expert parties agreed an evaluation of four options but they did not make a recommendation. It simply said, ‘Here is our risk assessment against each of these four options,’ and that was given to Scottish Government.

“We were then told we had to do nothing, the matter was being taken out of our hands. We were not to take any action until the Cabinet secretary had made her decision, nor were we allowed to communicate to anybody, internally or externally, including staff.

“We sat for the best part of a day biting our nails, then we got the announcement from on high, which basically said, ‘I have decided and I am overruling NHS Lothian’ that this move will not take place until we have 100 per cent assured ourselves the building is entirely safe in every possible dimension’. Nobody was arguing with the decision having been taken, but to come out and say she was overruling NHS Lothian was a lie.”

Former NHS Lothian chairman blasts: Jeane Freeman told lie over Sick Kids