An official review of the dance drug mephedrone was put back because of the fallout from the sacking of the Government's chief drugs adviser last year, it is claimed.
Liberal Democrat home affairs spokesman Chris Huhne has said "political meddling" by Home Secretary Alan Johnson had resulted in an "inordinate delay" in analysing mephedrone.
The sacking of Professor David Nutt led to the scientist in charge of looking at the effects of mephedrone to quit.
The Advisory Council on the Misuse of Drugs will report on the dangers to the government on March 29.
Home Office minister Alan Campbell said the Government is "determined to act swiftly" on the issue.
Meanwhile, police are investigating the deaths of Louis Wainwright, 18, and Nick Smith, 19, who were found dead on Monday. But say results of toxicology tests nay not be known for weeks.
Four men have been arrested and are being held in custody on suspicion of supplying a controlled drug.
