The health secretary has denied claims by a former health board chair of a “toxic” atmosphere between the Scottish government and senior NHS staff.

Former NHS Lothian chair Brian Houston resigned in January over “fundamental and irreconcilable” differences with Jeane Freeman relating to the delay to Edinburgh’s new Royal Hospital for Children and Young People.

In recent interviews Mr Houston said Ms Freeman had displayed “contempt” towards members of the health board’s senior team.

But speaking to MSPs the health secretary said: “I fundamentally disagree with Brian Houston’s reported assertions and accusations.

“I do not accept that there is a dysfunctional relationship in any respect. I accept that it is my job to challenge and support boards to ensure that we get the best performance for the investment.”

In response to questioning about whether Mr Houston was threatened with sacking if he did not quit, Ms Freeman added: “Mr Houston chose to resign; I chose not to use my ministerial powers.”

NHS Lothian’s chief executive Tim Davison is also stepping down in August after 26 years leading NHS boards.

Senior leaders at the board have faced criticism over the last-minute delay to the £400m Sick Kids hospital after safety checks picked up issues with ventilation at the critical care unit. Subsequent assessments revealed further problems across the building.

A review by management consultants KPMG said much of the delay related to NHS Lothian misinterpreting guidance about building regulations.