The Australian Criminal Intelligence Commission found cannabis seizures rose by 8 per cent in 2018-19 on the previous year - the highest percentage increase of the states and territories.

The ACT also had the highest percentage increase in the weight of cannabis seized.

According to the data, the number of cannabis seizures increased in the ACT from 608 in 2017-18 to 655 in 2018-19.

More than 340 kilograms of cannabis was seized, a 126 per cent increase from the previous year.

Cannabis-related arrests fell 44 per cent in the ACT, down from 338 to 188, but they accounted for nearly half of all illicit drug arrests in the territory.

The report covered the period prior to the ACT legalising small amounts of marijuana for recreational use.

The ACT government passed laws last year to allow Canberrans to possess up to 50 grams of dried cannabis or 150 grams of wet (or fresh) cannabis. Adults can also grow two plants at their place of residences. The laws came into effect on January 31 this year.

The Australian Criminal Intelligence Commission's Illicit Drug Data Report also found the nation's capital had the greatest percentage increase in the weight of cocaine seized. It was up 789 per cent but it was acknowledged this had come off a low base.

Only 652 grams had been seized in 2017-18 compared to 5798 grams in 2018-19. The number of cocaine seizures had also decreased from 152 to 127.

READ MORE:

ACT also had the greatest percentage increase in the number of steroid seizures (77 per cent) and other opioid seizures (63 per cent).

It is estimated that more than $3.5 billion of illicit drugs was seized in Australia over the year, Australian Criminal Intelligence Commission chief executive Michael Phelan said. As well, the number of illicit drug seizures increased by 77 per per cent over the past decade.

"It would appear that Australian drug markets continue to grow," Mr Phelan said. "As such, the importation, manufacture, cultivation and distribution of illicit drugs and related precursors in Australia remain focal points of government, law enforcement and intelligence agencies."

"These upward trends in national seizures and arrests highlight the continued vigilance of law enforcement in reducing the supply of all illicit drugs. They also highlight why illicit drugs continue to be a concern for law enforcement and the wider community, and the ongoing need to reduce demand."