HACKERS have attacked the website of South Australia's Family First party with a grim message vowing to ''irradicate (sic)'' them.

Information on the site about the party and its policies has been replaced with a warning message under the headline ''HACKED BY ANONYMOUS'', accompanied by an audio clip of a hip hop song by Australian band Dyad Souls.

''Your moronic backwards preaching will no longer be tollerated (sic),'' the message reads in red, all capped text.

''You claim to support family values - but all you support is bigotry. You encourage your children to grow up as ignorant as yourselves.

''You spread a message of hatred and lies to push your uberconservative agenda. You believe in the destruction of civil liberties, and the rise of a police state. For these crimes you have been judged to be non-worthy of your presence on our internet, and this action has been taken as a first step to irradicate (sic) this presence permanently.''

Tagged with the Twitter hashtag ''#opF***OffFamilyFirst'', which has seemingly not yet been used on the social network, the message ends with the traditional catchcry of internet activist group Anonymous: ''We are anonymous. We are legion. We do not forgive. We do not forget. Expect us.''

The hackers’ message has since been removed from the site, which remains offline as Family First SA attempts to restore it.

Family First SA member Robert Brokenshire was unaware of the hacking until called by News Limited this morning.

''It's a pretty senseless and undemocratic thing to do, isn't it,'' he said.

''I mean it's not an offensive website or anything, I don't know what their beef is but obviously they don't like something we've said or done.''

Mr Brokenshire said the party would investigate the attack.

Anonymous is an online activist group, or ''hacktivist'' group, which has a history of hacking government and security websites, most often as a protest against internet censorship and surveillance.

The changeable nature of the group and anonymity of its members means Anonymous is often cited in hacking attacks in which it has played no official part.

Responding to an inquiry by News Limited this morning, one Twitter account linked to Anonymous Australia, @AuAnon, tweeted the group knew nothing about the hacking.

Other Facebook and Twitter accounts linked to the group have so far made no mention of the attack.