Concerns have been voiced over the vaccine
The findings of the group of Scottish experts should have been made public at the end of this month.
However, the Scottish Executive has said that this will now be delayed by "a matter of weeks."
The Scottish National Party said the development was unfortunate.
And the party's health spokeswoman Nicola Sturgeon voiced concern over reports that the group was likely to make a majority recommendation to continue to give parents no alternative to the triple vaccine.
The expert group was set up last year following a recommendation by the Scottish Parliament's health committee.
The MSPs' investigation was sparked by a petition from a campaigner who believes his grandson developed autism after being given the MMR jab.
The committee found no proven scientific link between the vaccine and the condition - but said it had concerns it wanted addressed.
It wanted answers to questions such as what could have caused the steep rise in autism if it was not the MMR vaccine, and whether a choice of single vaccines would increase or decrease the uptake of the triple jab.
Gathering evidence
Dr Bill O'Neill of the British Medical Association said he was not worried by the delay in publication of the report, which he said was not unusual.
However, he said he was concerned children were not being immunised against what can be killer diseases.
The Scottish Executive said the process of gathering evidence had been very extensive, which accounted for the delay.
The expert group includes representatives from a wide range of organisations including the Scottish Society for Autism, the Scottish Consumer Council, the Medical Research Council and the Royal College of Paediatrics and Child Health.
Parental concerns
There have been reports that the group was deeply divided over whether to offer parents a single vaccine in the face of a drop in MMR inoculation rates across Scotland.
Ms Sturgeon said it was "unfortunate" that the report had been delayed.
"What is even more concerning is the suggestion that the report is going to be nothing more than a whitewash and it is going to recommend the status quo should remain despite considerable parental concerns.
"What the report must do is build confidence in the immunisation programme," she said.