Police are calling for the controversial Rainbow Serpent Festival to be cut back, saying it poses an "extreme" safety risk.

A 22-year-old man died at the festival near Lexton in central Victoria, which this year ran for five days in late January. Two sexual assaults, six drug trafficking charges and four road crashes were reported in relation to the event. Police said one in eight drivers tested for drugs returned a positive result.

Rainbow Serpent Festival. Credit:Francesco Vicenzi

Ballarat's Superintendent Andrew Allen said the festival posed "extreme risks" to other road users. He said he would "categorically be agitating for a reduction in the length of the festival".

"This elevated rate of positive tests from the event is completely unacceptable and something has to change," he said. "More responsibility must come from the festival organisers in relation to the impact this has on the community."