Police have launched a stinging attack on electronic music festival Rainbow Serpent, labelling behaviour at the bush dance event "completely unacceptable" after the death of a reveller on the weekend.

A 22-year-old Kensington man died about 10pm on Saturday after emergency services were unable to resuscitate him after he collapsed during the festival which was held on farmland near Beaufort in western Victoria.

A scene from last year's festival, during which 40 attendees were arrested. Credit:Francesco Vicenzi

Despite repeated warnings, police said they dealt with a string of serious offences at this year's event, including two sexual assaults, six incidents of drug crimes and 17 drug-driving offences.

Ecstasy, MDMA, ketamine and cannabis were among the drugs seized by police.