Scotland's biggest health board should be put in "special measures" over its handling of hospital infection issues, according to an MSP.
Anas Sarwar made the call after a mother accused NHS Greater Glasgow and Clyde (NHSGGC) of covering up possible factors in her daughter's death.
Mr Sarwar said the health board had tried to intimidate health service whistleblowers who had raised concerns.
NHSGGC said the source of the child's infection could not be determined.
Earlier this week a whistleblower revealed that a doctor-led review had identified 26 infections at Glasgow's Royal Hospital for Children in 2017 which were potentially linked to problems with the water supply.
Kimberly Darroch, whose daughter Milly Main died at the hospital in August 2017 while in remission from leukaemia, said health officials gave her no inkling that contaminated water could have been a factor.
Health Secretary Jeane Freeman has said the first she knew of Milly's death was when Ms Darroch emailed her about her concerns in September.
NHS Greater Glasgow and Clyde has offered to meet the family to discuss their concerns - but said it was impossible to accurately determine the source of Milly's infection because there was no requirement for water testing at the time.
It said the hospital's water had been independently assessed as safe, and it criticised the whistleblower for causing "stress and anxiety" for Milly's parents when there was no evidence of a link.
Anas Sarwar, however, insisted the health board had let down both patients and staff.
He said: "There was an attempted cover-up of Milly's death, and there are still dozens of families who don't know the truth about infections contracted in the QEUH.
"This only came to light following the brave actions of an NHS whistleblower. But rather than seek answers for patients and the public, the health board resorted to attacking the whistleblower, threatening and intimidating them."
The Labour MSP said Health Secretary Jeane Freeman only knew about Milly's death because she was contacted by her mother "despite health chiefs at the board knowing since the doctor-led review earlier this year".
Ms Freeman has ordered a public inquiry into issues at the Glasgow "super hospital" site and Edinburgh's new children's hospital - but Mr Sarwar said more urgent action was needed.
He said: "The Scottish government must now step in and put the health board into special measures, so that ministers take control, staff can speak out in confidence they will not lose their jobs, and - most importantly - parents can learn the truth."
The £842m Queen Elizabeth University Hospital (QEUH) opened in 2015 and the campus includes the adjoining Royal Hospital for Children.
Two cancer wards at the children's hospital were closed last year amid concern about infections, with patients decanted to the adult hospital.
In January it emerged that two patients at the QEUH had died after contracting a fungal infection linked to pigeon droppings.
'No way to know'
NHS Greater Glasgow and Clyde said in a statement: "We are sorry for any distress and anxiety being caused to families at this time.
"The truth is there is no way to know whether Milly's infection was linked to the water supply as we did not consider this to be the source at the time and we did not test for the particular infection in the water supply.
"A potential link between infections and the water supply only emerged the following year and this was confirmed earlier this year when Health Protection Scotland published their report on their investigations.
"We acted on this report and put in place extensive measures to improve the water supply, which is safe.
"We are absolutely committed to providing patients and families with information and ensuring they get answers to the questions they have; it is really important that we base these answers on the facts."
A spokesman said they were working with Professor Craig White, who was appointed by the cabinet secretary to provide support for families.
"We always have to take care when discussing our patients not to breach their rights to confidentiality," she added.
"This can make it difficult to discuss in detail individual cases but we wish to make clear that we are taking these matters extremely seriously."
The health secretary intends to make a statement to Ms next week on the issue of infections at the hospital.
She said: "I have been clear with NHS Greater Glasgow and Clyde that their approach to engagement with affected families had not been good enough, and they have sought to improve how they do this."