Mr Hanson said the community wanted tougher penalties for unprovoked, serious criminal assaults known as "coward's punch" attacks. Changes to the Crimes Act would see the creation of a new aggravated offence to deal with one-punch attacks and tougher penalties for a range of offences including grievous bodily harm, assault and affray.

The move comes after a series of one-punch attacks and drunken assaults around Canberra's busiest nightspots and in other Australian cities in recent months. Last year ACT Attorney-General Simon Corbell ruled out introducing new offences, or mandatory minimum jail sentences, for one-punch attacks and other forms of alcohol-related violence.

The opposition's draft legislation is set to be introduced into the Legislative Assembly's first sitting period next month and shared with community groups and victims' advocates for feedback. It would apply to an attacker who hit another person without provocation. Penalties for assault would apply even if a one-punch attack could not be proven.

Mr Hanson said he would seek to win support for the plan from the government or from Greens Minister Shane Rattenbury in coming months, but was prepared to take the issue to October's territory election.

The draft legislation is the opposition's first new policy announcement in the election year and comes as Chief Minister Andrew Barr reshuffles his front bench.

Mr Hanson said the proposed law was tougher than across the border in New South Wales, where one-punch laws only involved death and required perpetrators to be drunk.

"This is designed to send a very clear message to the community. We will take action if the government won't.

"The penalties will be significant. If you kill somebody, it means the maximum penalty can be 25 years which is the same as murder. If you are found guilty of assault or other serious crimes, you will also face much tougher penalties."

Anyone found guilty of recklessly inflicting grievous bodily harm through a one-punch attack would face 15 years in prison. Wounding another person could attract seven years while common assault and affray would both attract three years prison.

"We know a lot of these coward punches leave people with serious injuries, often people are left with brain injuries," Mr Hanson said.

"We've have been looking at this legislation for a while. Clearly there is a call from the community for Assembly members to act.

"This will make a difference. It sends a very clear message that if you perpetrate a coward's punch, the penalties are significant."

The Australian Federal Police Association, which represents ACT police, has previously called for the introduction of specific one-punch laws, similar to those in Victoria and NSW.

In 2015, Mr Corbell said several existing offences in the Crimes Act covered actions that could see offenders charged for one-punch attacks. The offence a person was charged with depended on the individual circumstances of the crime, Mr Corbell said.

Existing maximum penalties ranged from two years in jail for common assault to life imprisonment for murder.