An expert review on the effects of mephedrone could be delayed until the autumn, the Today programme understands.
The report, from a sub-committee of the Advisory Council on the Misuse of Drugs (ACMD), is expected to advise the government whether there is any evidence that the drug, currently legal but blamed for a number of deaths, is harmful.
But the review, which was due to have been completed this month, has been delayed following the sacking of the ACDM's head, Professor David Nutt, and the resignation of other members of the committee following Prof Nutt's criticism of government drugs policy.
The Today programme's science correspondent Tom Feilden said that it was not certain that the reconstituted sub committee has the experience needed to rule on the drug.
The National Association of Head Teachers have called for an urgent government response over the drug, which they say is being used by children as young as nine.
Speaking on the programme consultant toxicologist Dr David Wood, the UK's leading medical expert on mephedrone, said that although it was not yet understood quite how dangerous the drug was, it had been linked to "significant acute health effects", including fast heart rates and and seizures.