Australian Federal Police Association president Angela Smith said the bill, which was introduced in the ACT Legislative Assembly on Wednesday, did not explore issues of the health system, therapeutic controls and how to deal with those found driving under the influence of cannabis.

The bill, a major reform that would make it legal for adults in the ACT to possess up to 50 grams of cannabis or four cannabis plants, was introduced by Labor backbencher Michael Pettersson.

The amendment would change the definition of an offence relating to the use of cannabis under the Drugs of Dependence Act 1989, and remove the drug from the definition of a prohibited substance.

But it does not mention any changes relating to driving laws, safe drug supplies or types of plant - issues that have been raised in previous days by members of the legal and medical community.

It is currently illegal to drive with any cannabis in your system.

Ms Smith said while people using cannabis in private and in small quantities did not currently place a significant burden on the criminal justice system in Canberra, making the drug legal would prevent police from accessing those who may need help within the health system.

Ms Smith said such a change in the law would need extensive discussion before it was enacted.

“This is not a simple fix,” she said.

“There is a broad-ranging discussion that needs to take place.”

The bill has the unanimous support of government MLAs, while Greens parliamentarian Shane Rattenbury supports the bill in principle but wants to wait until it is debated in the Assembly before giving it his full support.

But despite several questions remaining unanswered relating to the finer details of the bill, Labor and the Greens want to push the law through as soon as possible, opting to go straight into a debate during the next sitting period in February, rather than referring it to a committee for an inquiry.

In the meantime, ACT police chief Ray Johnson reiterated that the current road safety laws were unlikely to change under the proposed legislation.

“ACT Policing strongly discourages drivers using any substance that impairs their ability to safely control a vehicle and then driving on a road or road-related area in the ACT,” he said.

“Under current legislation, it is illegal to have any trace of illicit drugs, including cannabis, in your system while driving a motor vehicle.

“Road safety is important and I don’t envisage that these provisions will change under the proposed legislation.”

Mr Pettersson argued on Wednesday the bill itself, which he believed had the support of most Canberrans, was simple and short, and did not need a committee or more time to debate its merits.

“This bill was first unveiled about two months ago. We've had two months to look over a small document, a tiny document, something like 10 pages in it, you could read it whilst I'm talking now,” he said.

“The idea that we don't have enough time in those months to think about this and engage with the community is ludicrous.”

But ACT shadow attorney-general Jeremy Hanson, who opposes the bill, pointed out that the length of the bill was irrelevant to its potential effects on various other laws and regulations.

For instance, he said, in a submission to the draft exposure bill earlier this month, the ACT branch of the Australian Medical Association strongly opposed the bill, citing the drug's harmful effects on certain sectors of the community.

“There are some real concerns raised by the AMA about the effects of cannabis on people, and the potential consequence of legalising cannabis for personal use, and I think we should take pause to consider what they have said,” he said.

“I see that there's nothing lost in us gaining a better understanding of this issue. There is nothing in terms of time limits that requires us to smash it through with any degree of urgency.”

Mr Rattenbury accused the Liberals of employing stalling tactics to prevent the bill from being enacted into law.

“I think that for too long, people have been criminalised for personal possession of cannabis, and I just don't think that it is appropriate that that continues to be the case. The Greens will be supporting this legislation," he said.

"I think there is plenty of time for people to consider this issue over the summer recess, to form a view on it, to seek expert advice and when we come back here next February we can debate this, and that is the position we intend to take.”

Mr Pettersson told The Canberra Times that while it would remain illegal to have cannabis in your system while behind the wheel, he was hopeful about "exciting technologies"being developed in the US that would make it easier to detect recent cannabis use.