Cannabis use may be legalised in the UK if the government adheres to recommendations made in a new report by the UK Drug Policy Commission (UKDPC).

The report, entitled A Fresh Approach to Drugs, suggests that cannabis possession should be made legal and people should be able to grow the plant for personal use.

Every year, 42,000 people in England and Wales are sentenced for drug possession offences, while 160,000 are given warnings about cannabis.

The UKDPC says these warnings lead to a great amount of time and money being spent by police. They also damage many people's employment prospects. It says there is evidence to show that these costs could be reduced by allowing people to possess small amounts of cannabis for personal use.

According to the report, evidence from other countries suggests that legalising cannabis would not necessarily lead to a significant increase in use.

In 2009 cannabis was reclassified from a class C drug to a class B. The maximum penalty for possession is five years' imprisonment, but many first-time offenders and young people are issued with warnings.

Half of all 16 to 29-year-olds say they have tried cannabis at least once and around two million people are thought to smoke it.

However, research over recent years has strongly suggested a link between cannabis use and mental health problems in people who are genetically vulnerable. Studies have shown cannabis users have a higher risk of suffering from depression, anxiety and developing schizophrenia.

The report said: "We do not believe that there is sufficient evidence at the moment to support the case for removing criminal penalties for the major production or supply offences of most drugs.

"However, for the most ubiquitous drug, cannabis, it is worth considering whether there are alternative approaches which might be more effective at reducing harm.

"For example, there is an argument that amending the law relating to the growing of it, at least for personal use, might go some way to undermining the commercialisation of production, with associated involvement of organised crime and the development of stronger strains of cannabis ('skunk'), that we have seen in the UK and other countries in recent years."

The report also pointed to the fact that some people will experiment with drugs, and some will continue to use, despite being aware of the risks. It said that preventing drug use in all circumstances is not required to encourage responsible behaviour.

"This is not to say that we consider drug use to be desirable," it said. "Just like with gambling or eating junk food, there are some moderately selfish or risky behaviours that free societies accept will occur and seek to limit to the least damaging manifestations, rather than to prevent entirely."

Last week, an elderly couple from Bedford unwittingly grew a huge cannabis plant in their back garden. Bedford police tweeted: "Elderly couple bought shrub at car boot sale, tended carefully-biggest cannabis plant we had seen!!"

A spokesperson said the plant had been collected and would be disposed of. No police action was taken against the couple.