Sir Richard Branson will tell MPs on Tuesday that the government should consider decriminalising drugs.

The war on drugs has failed and alternative, fact-based approaches are needed to reduce the harm caused by narcotics, the tycoon will say.

Sir Richard will be among the first to give evidence as the Commons Home Affairs Select Committee launches the first parliamentary inquiry into drugs policy for more than 10 years.

It comes as new guidelines for sentencing in drugs cases were issued to judges.

So-called drug mules, who bring narcotics into the country and are often exploited by organised criminals, could serve less time in prison from next month under the guidelines, which were set by the Sentencing Council.

It has also been reported that clinical trials of "magic mushroom therapy" could take place in the UK within a year following two ground-breaking studies.

Professor David Nutt, the former government drug advisor who was sacked for criticising the decision to toughen cannabis laws, has said it was a mistake to have abandoned research into the medicinal use psychedelic drugs.

The previous Commons inquiry in 2002, when David Cameron was on the committee as a Tory MP, said drug use was a "passing phase" for many young people which "rarely results in any long-term harm".

The cross-party group dismissed legalisation and decriminalisation as a way forward but, paving the way for future changes, urged ministers to lobby for the loosening of international treaties which prohibit such radical steps.

Speaking more than 10 years ago, Cameron added that the UK's drugs policy "has been failing for decades" and said he hoped the report "will encourage fresh thinking and a new approach".

But the Home Office has already said it has "no intention of liberalising our drugs laws".

Sir Richard is a member of the Global Commission on Drug Policy, whose members include former United Nations secretary general Kofi Annan.

It warned in June last year that major policy reforms were needed to help reduce the prison population and stop wasting millions of pounds.

Dame Judi Dench was among a host of high-profile stars to back the call, saying an "immediate decriminalisation of drug possession" should follow if a policy review showed it had failed.

The government's official drugs advisers have also called for possession to be decriminalised.

The Advisory Council on the Misuse of Drugs (ACMD) said there was an "opportunity to be more creative" in dealing with those accused of possessing drugs, sending them on awareness courses rather than charging them with criminal offences.

Ruth Dreifuss, the former president of Switzerland, will also give evidence to the MPs today.

Keith Vaz, the committee's chairman, said: "We will be talking to a number of people during what is sure to be a long-running inquiry.

"I look forward to hearing the commission's evidence on why the war on drugs has failed and why it is now time to decriminalise drugs and focus on providing treatment to drug users in a bid to bring an end to the destructive cycle of addiction."

He added: "Drugs can be a hugely controversial issue but we hope that this will be the start of a balanced, well-reasoned inquiry."