PROTECTING children online could be harder with a mandatory internet filter in place, a coalition including state schools, librarians and key players in the internet industry has warned.

The recently formed Safer Internet Group argues that the federal government's proposed filter is a simplistic solution to shielding children from harmful content on the internet.

''We believe that real online safety can be delivered without the implementation of a mandatory internet filter, which locks parents and the industry out of keeping kids safe online,'' the group wrote in a submission to a parliamentary committee on cyber safety.

''The mandatory filter gives parents a false sense of security regarding online safety.''

The group's membership includes the Australian Council of State School Organisations, the Australian Library and Information Association, the Internet Industry Association, Google, Yahoo! and iiNet.