As a Labour loyalist I seldom vote against the government – in fact there are three occasions when my conscience has led me to rebel since my election to Westminster. I am often asked about my position on the Iraq war, and my view on that remains unchanged. The other issue is cannabis and my opposition to the reclassification of the drug from a class B to a class C drug is on record, as are my reasons. I was therefore delighted that this government has been brave enough to reverse that decision. For the same reason I voted against the government the first time, I support its policy now.

One of the main reasons I believe we shouldn't alter the present classification of drugs is the danger of misuse among young people. We would not be sending out the right message that drugs are dangerous, and there is no way any responsible body should suggest otherwise.

Medically, the earlier people take up smoking and drinking, the more vulnerable their brains are to the long-term effects of the substances. In regards to cannabis, there is also strong evidence of a link between the adverse effects it has on long-term mental health and the fact that most young people attending psychiatric clinics are regular or occasional cannabis users.

When you combine this with the massive growth in the availability of the form of cannabis known as skunk in the last few years, then the government decision becomes a no-brainer. According to the Home Office, skunk accounts for 70-80% of the cannabis sold on the streets of Britain, compared with just 15% in 2002. Skunk contains three times the levels of THC of regular cannabis, which has levels of only 2%, according to the charity Drugscope. This stronger version of the drug can also bring about psychotic attacks, even in those with no previous psychiatric history.

This different form of cannabis is not only stronger but also more damaging to the developing brains of our children. Especially considering that the average age at which users first try skunk is now only 13. The National Treatment Agency (NTA), a special health authority within the NHS established by the government, has monitored the drug use of under-18s since before and after the first reclassification. Its 2003-04 report shows that 61% of those aged under 18 claimed cannabis to be their main problem drug. In its latest figures, from 2008-09, the NTA says 78% of its clients claim that cannabis was their main drug of misuse.

The more traditional versions of cannabis are not much better. A puff of smoke from a joint of cannabis contains the same components as that of tobacco, and the concentration of carcinogens in cannabis smoke is actually higher than in cigarettes. In fact, smoking 20 cigarettes is the equivalent to smoking three joints a day.

If you examine so-called factual scientific evidence over many years, you will find on many occasions conflicting evidence and often different conclusions reached. Long-term examination of scientific evidence often changes previous conclusions, and while scientists have a right to express their view based on their assessment of the evidence they believe is sound, they are not infallible.

I have a simple view – reclassification of cannabis sent out the wrong message, it caused considerable confusion and a belief among young people that it was safe, that smoking it was no longer a criminal act and that it was not dangerous. We must err on the side of caution when we legislate, especially when we are dealing with the health and welfare of our future generations. If Prof David Nutt is happy to allow his children to use drugs such as cannabis so be it, I fundamentally disagree with his position as a father and as a politician. Nutt has the right to form his conclusions on drugs, he had the right to voice his disagreement, but the honourable option he should have taken, if he fundamentally disagreed with the political decision, would have been to resign, and be free to argue his own position.

The Nutts of this world are so far removed from the tertiary impact that such drugs have on constituencies like mine that their outlook towards cannabis on a social level resembles Woodstock rather than Whiteinch. Therefore, I agree with Alan Johnson – horse riding will not affect my constituents either, as there are more "cannabis farms" in my constituency than stables. So until equestrianism outranks drug-taking in the poorest parts of this country, it should be higher up the government's agenda on dangers that we should be protecting our children from.