Australians are using cocaine at some of the highest-ever recorded levels, according to new stats.

The National Drug and Alcohol Research Centre's (NDARC) has released its 2018 Drug Trends report, which is based on hundreds of interviews with drug users in Australia's capital cities.

It found that 59 per cent of respondents reported using cocaine in the past six months, up from 48 per cent in interviews from 2017 and its highest level since 2003.

One in four respondents (27 per cent) reported using ecstasy at least once in the last six months.

Among ecstasy users, consumption of the higher-purity crystal form has reached 72 per cent and capsule form is up to 62 per cent.

Nine out of 10 participants reported using depressants like cannabis and alcohol or hallucinogens such as psychedelic mushrooms and LSD the last time they used a stimulant.

“It is of concern, particularly when people are using over a long period of time or when people are mixing these stimulants with other substances,” Dr Amy Peacock, a career fellow at the NDARC, said in a briefing on the survey.

Seven per cent of respondents used cocaine at least once a week.

“When we asked participants about the perceived availability of cocaine, 62 per cent of consumers said they thought it was ‘easy’ or ‘very easy’ just to obtain,” Dr Peacock said.

One in five people surveyed reported buying drugs on the internet.

“20 per cent of those surveyed told us they purchased substances online in the past year, primary from dark web marketplaces,” NDARC Senior Research Officer Rachel Sutherland said.

Over 50 per cent of participants reported using LSD in the past six months, while 35 per cent said they had used ketamine during the same period.

Eighteen per cent reported consuming capsules with unknown contents in the past six months.

A full report on the findings is available in PDF form, here.