Melbourne streets are being deprived of hundreds of police officers because of radical protests.

Police documents obtained by the Herald Sun show 888 officers were taken off the beat to separate opposing activists across three protests last year, at a cost to Victorians of an estimated $310,000.

Hundreds of police lined St Kilda Beach on Saturday to control warring far-right protesters and anti-racism activists.

Click PLAY for vision from Saturday and radio report

Force command is concerned a rally next month, involving a trio of controversial right-wing figures, could be the most resource-draining event yet.