Following the completion of the parliamentary process on 12 April, mephedrone and other cathinone derivatives are now illegal as Class B drugs.
Class B drugs carry a maximum prison sentence of five years for possession and a maximum prison sentence of 14 years for supplying and other trafficking offences.
But an editorial in The Lancet has criticised the Advisory Council on the Misuse of Drugs (ACMD) and the Home Office's steps to ban the drug.
It also believes the ACMD documented ‘very scanty' evidence to form a direct causal link between reported deaths and the drug.
‘There was little time to consider carefully the scientific evidence on mephedrone. The ACMD did not have sufficient evidence to judge the harms caused by this drug class,' The Lancet said.
‘It is too easy and potentially counterproductive to ban each new substance that comes along rather than seek to understand more about young people's motivations and how we can influence them.'
The editorial added: ‘We should try to support healthy behaviours rather than simply punish people who breach our society's norms.'
It also suggested that making the drug illegal will deter crucial research on the drug and other drug-related behaviour, making it more difficult for people with problems to get help.
The editorial concluded: ‘Politics has been allowed to contaminate scientific processes and the advice that underpins policy. The outcome of an independent enquiry into the practices of the ACMD, commissioned by the Home Office in October, 2009, is now urgently awaited.
‘Lessons from this debacle need to be learned by a new incoming government.'