Ministers want to send a message that cannabis use is unacceptable
The government insists it is responding to public concerns about the health risks of cannabis in wanting to reclassify it. BBC home editor Mark Easton considers what prompted this stance by ministers.
Politicians know it is electoral suicide to appear "soft" on the issue of drugs. People want something done.
Last October, Gordon Brown told his party conference about his strategy. "My answer," he said, "is to punish the evil of drug pushers who poison our children."
The trouble is that punishment has failed to solve the problem.
Britain has among the harshest and most punitive drug enforcement in Europe, the highest per capita prison population in Europe and its levels of drug use and drug deaths are consistently among the highest in Europe.
The link between criminal sanctions and drug use is far from straightforward.
Indeed, when cannabis was downgraded, there was actually a significant fall in its use, suggesting a drug's classification is not the trigger for changing behaviour.
Nevertheless, the government wants, in its words, to send a message that cannabis is "unacceptable".
Reclassifying it as class B in defiance of the official advice is just that - a message.
In practical terms, it will change little. Those caught with cannabis could face five rather than two years in prison.
But police have said they are unlikely to alter their current strategy - treating possession as largely a non-arrestable offence.
So the question perhaps is: "To whom is 'the message' really aimed? Drug users or voters?"