Health experts have expressed concerns that the first parliamentary inquiry for 10 years into Britain's policy on illegal drugs will start by accepting testimony in favour of decriminalisation from Sir Richard Branson.

The decision by the home affairs select committee's inquiry to summon the Virgin tycoon as its first witness has raised eyebrows among some health and legal experts. Branson will appear along with Ruth Dreifuss, the former president of Switzerland. Both are commissioners for the Global Commission on Drug Policy, a respected organisation supported by George Shultz, the former US secretary of state, and former presidents of Mexico, Colombia and Brazil.

The commission – which is also backed by celebrities including Sting, his wife Trudie Styler, Julie Christie, Dame Judi Dench and Kathy Burke – published a report last year declaring that the "war on drugs" had failed, and recommending a new international approach.

The inquiry, which calls its first witnesses on Tuesday, is expected to be extremely broad, examining law reform, decriminalisation, classification, the growing use of "legal highs" and the efficacy of treatment programmes. It is expected to issue findings before the end of the year. The last committee inquiry into drugs published a report – supported by its members who included a youthful David Cameron – calling on the government to examine legalisation and the regulation of illegal substances.

The choice of witnesses for the new inquiry has buoyed hopes among reform campaigners that it will conclude there is a need to overhaul Britain's drug policy. But there are concerns among some experts that the focus on a celebrity-backed decriminalisation campaign could risk playing down more immediate problems.

The ringfencing of drug and alcohol treatment budgets ends in April next year and there are serious concerns among health professionals about the impact that this will have on curbing addiction rates. It is understood that the Department of Health has reservations about ending ringfencing. There are also concerns in the Home Office and the Ministry of Justice. "Is the committee going to focus on decriminalisation when the more immediate problem is what is going to happen next year when local authorities are having to make 25% cuts?" said one drugs expert who asked not to be named. "The government might not mind too much if the focus is on legal issues rather than cuts."

The committee has invited high-profile individuals in the past to give evidence. Mitch Winehouse, the father of the late Jazz singer Amy, gave evidence in 2009 when it was investigating the cocaine trade.

"I am delighted that Sir Richard Branson… will be presenting evidence to the committee alongside the former Swiss president Ruth Dreifuss," said Keith Vaz, the chair of the committee. "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."

Branson has become an eloquent spokesman for the pro-reform camp. In a speech last year, he said: "Our commission found that in countries where drug addiction was decriminalised and regarded as a public health problem, there were decreases in crime, decreases in the number of addicts, and improvements in overall public health."

He cited the example of Portugal, which decriminalised the use and possession of drugs in 2001. By setting up clinics where heroin users have access to needles and methadone, along with addiction treatment, Portugal has reduced the number of users, especially among young people.

Vaz has indicated that the inquiry will address all aspects of drug policy. "We will be talking to a number of people," he said. "Drugs can be a hugely controversial issue but we hope that this will be the start of a balanced, well-reasoned inquiry." The committee will also hear evidence from the UK Drug Policy Commission an independent body providing objective analysis of Britain's drug policy. The commission has recently investigated the new wave of psychoactive substances, better known as "legal highs", as well as the effect of austerity measures on UK drug policing.