The decriminalising of cannabis will be examined by MPs as part of an unprecedented investigation into Britain's drugs laws.
The Home Affairs Select Committee, in its first major inquiry of the new parliament, will consider the effectiveness of government policies in combating drug addiction.
The decision to venture into such politically contentious territory follows increasing pressure from politicians of all parties who want a fresh look at the laws on drug use.
David Blunkett, the Home Secretary, marked a shift in government attitude this month by saying he was prepared to consider the arguments for decriminalising soft drugs.
The committee will take evidence from Mr Blunkett and Lord Irvine of Lairg, the Lord Chancellor, as part of its investigation, which is scheduled to begin in October.
It will consider the effect that relaxing controls on cannabis use would have on the demand for drugs, drug-related deaths and crime levels. It will examine the desirability of such a step and look at the practical alternatives to decriminalisation. Itwill also examine the laws on class A drugs such as heroin, cocaine and ecstasy.
Chris Mullin, the committee chairman, said yesterday: "There is a big debate going on outside parliament among serious people in the criminal justice system, including senior police officers, probation officers and members of the judiciary. Until now, politicians have tended to shy away from it but we think the time has come for a serious assessment of the way we deal with drugs.
"We have an entirely open mind so we're not headed for any particular conclusion but we hope to bring all different arguments into the open."
Harry Shapiro, a spokesman for the charity DrugScope, said: "We have seen evidence in recent weeks that more politicians are ready to take on this complex issue and explore the possibilities for change.
"An open and mature debate could help re-engage many, particularly the young, in the political process."
The issue moved to the centre of political debate three weeks ago when Peter Lilley, a former Tory deputy leader, floated the idea of allowing the sale of cannabis in licensed stores. Sir David Ramsbotham, the outgoing chief inspector of prisons, has also said he supported legalisation.
Mo Mowlam, who as Cabinet Office Minister was in charge of drugs policy, and Keith Hellawell, the Government's anti-drugs co-ordinator, have called for debate on the subject.
Police in Brixton, south London, have said they will no longer arrest people found using cannabis, a change of policy that supporters of legalisation believe will lead to a more relaxed attitude to the drug by forces around the country.