A cot death expert has raised safety concerns about baby boxes, according to a report.
Peter Blair, who chairs an international body on the study of infant deaths, urged the Scottish Government to stop advocating the box itself as a default place to sleep.
The Bristol academic said it should only be promoted for that purpose as a last resort.
Scottish ministers, backed by the country’s chief medical officer Catherine Calderwood, have repeatedly said the box is “designed to provide a safe sleep space for babies”.
In a draft statement sent to the SNP administration, Mr Blair also warned that the unlaminated boxes could be potential fire risks.
And the British Standards Institute cast doubt on claims the box has full safety accreditation, according to the report in The Guardian.
The boxes are distributed for free to every newborn in Scotland and have been widely praised.
They contain clothes, changing mat, thermometer, books and bedding and ministers say the box can be used as a cot.
Dr Blair, who is based at Bristol University’s medical school, is chairman of the International Society for the Study and Prevention of Perinatal and Infant Death (Ipsid).
According to The Guardian, he told the Scottish Government in a statement to stop supporting their use as a cot except in emergencies.
“They shouldn’t be advocating infants sleep in these boxes unless there isn’t anything else available,” Dr Blair said.
In the memo, he added: “I’m not saying don’t use the baby box, I’m just saying that you’ve got to be careful with the advice of how much you can promote it as a safe sleeping space.
“I think there’s possibilities there but there’s much room for manoeuvre and they’re pushing it too far at the moment.”
The Guardian has reported that despite government claims that the box is the first non-commercial cardboard baby box in the world to be given safety accreditation, the BSI says that status is not yet available for the boxes in the UK.
The newspaper reported the BDI was only now starting work on designing that accreditation.
Miles Briggs, the Scottish Conservative shadow health secretary, said there are “extremely serious questions for the SNP Government to answer here”.
“Parents have been told time and again by Nicola Sturgeon and her ministers that baby boxes are safe,” the MSP said.
“Now we learn that a senior expert has raised questions about the evidence base for that in private, and that there are doubts over whether the boxes have the full safety accreditation.
“Why has is taken only now for these concerns to be raised in public? And why, initially at least, did the Scottish Government fail to take Mr Blair’s concerns on board?
A Scottish government spokeswoman said the boxes are safe and fully approved.
“There is no evidence to suggest the baby box is unsafe and we are in ongoing discussions with Peter Blair about his concerns,” she said.
The baby box meets British safety standards and was awarded British safety standard accreditation as a crib for domestic use – the first non-commercial box in the world to do so.”
“We will ensure that Scotland’s baby box complies with the new standard once it is developed.
“As the material issued with the baby box makes clear, the baby box – and its associated bedding – is intended to offer a safe sleeping place when used in accordance with other safe sleeping practices.”
