An online activist group will use a flash mob on April Fools Day to raise its concerns about the Internet content filter to the general public.

The Sydney Anti-Filter Coalition, one of many splinter groups opposed to the Federal Government’s plans to provide a mandatory ISP-level internet filter, is urging its supporters to gather in Sydney’s central business district for a flash mob event. Participants will wear gags and hand out information to the general public.

It will be the first use of flash mobs — a favourite of pranksters and first coined by Harper’s Magazine editor Bill Wasik — by content filter activist groups, although rallies have been staged around the country since the proposal’s inception in 2008, with moderate success at best.

The Perth chapter of a set of rallies staged in Melbourne, Brisbane, and Sydney last Saturday attracted up to 300 supporters, according to StopTheFilter organiser, Trish Zanetti. Melbourne attendees reported more than 100 people, while numbers were said to be low at Parramatta and Melbourne.

The flash mob event will be promoted via Twitter and Facebook, despite some supporter claims the websites are ineffective at pushing awareness to the uninformed general public. Organisers ask that the event be promoted only under #openinternet or #nocleanfeed on Twitter and Identi.ca services and have called for street crews to distribute posters around public areas.

Opposition groups could unify under the Net Freedom Coalition, according to decisions made by an organiser at the Parramatta rally on Saturday.

Recent polls suggest that the filter scheme has widespread support in the general public yet vehement opposition in the IT industry. A McNair poll of 100 people by the ABC’s topical news television program, Hungry Beast, found that 80 per cent of the general public support the initiative with 94 per cent in favour of government moves to protect children from exposure to inappropriate material online. A survey by popular telecommunications website Whirlpool, however, found 92.6 per cent of 23, 683 of its website members, including a large proportion of IT workers, rejected the plan with about half reporting it could influence their vote in the Federal election.

Facebook pulled off a successful flash mob event promoted on its site last year in Sydney. About 500 people turned up, less than the anticipated 2500, to bemused and confuse people by freezing for three minutes in various positions in Martin Place and Pitt St Mall in the CBD. The final location for the event was revealed in the dying hours to maintain secrecy as wristwatches were synchronised in a Hyde Park gathering.