ABC chairman Jim Spigelman has strongly criticised the federal government's proposed anti-discrimination law, saying it poses risks to freedom of speech.

Mr Spigelman, former New South Wales chief justice, said there was no justification for including the notion of ''offending'' in the definition of discrimination.

The legislation consolidates several anti-discrimination laws, including that on racial discrimination, which refers to treatment that offends. The proposed law extends ''offending'' into the definition of discrimination for all purposes.

Delivering an oration on Human Rights Day, Mr Spigelman pointed out that none of the other existing Commonwealth acts - covering sex, disability and age discrimination - included conduct that only offended.

The freedom to offend was an integral component of freedom of speech. ''There is no right not to be offended. I am not aware of any international human rights instrument, or national anti-discrimination statute in another liberal democracy, that extends to conduct which is merely offensive,'' he said.

''We would be pretty much on our own in declaring conduct which does no more than offend, to be unlawful,'' Mr Spigelman said. ''This should give us pause.''

Mr Spigelman made it clear he did not agree with the judgment against journalist Andrew Bolt in 2011 under the racial discrimination law, when the judge said: ''I am satisfied that fair-skinned Aboriginal people (or some of them) were reasonably likely, in all the circumstances, to have been offended, insulted, humiliated or intimidated by the imputations conveyed by the newspaper articles.''

The proposed law defines discrimination by unfavourable treatment to include ''conduct that offends, insults or intimidates'' another person because the other person has a particular protected attribute.

Mr Spigelman said words such as ''offend'' and ''insult'' impinged on freedom of speech in a way that words such as ''humiliate'', ''denigrate'', ''intimidate'', ''incite hostility'' or ''hatred'' or ''contempt'' did not.

Unlike the existing racial discrimination law, ''there is no element of objectivity, as presently found in the words 'reasonably likely to offend'''. The new bill appeared to contain a subjective test of being offended.

Mr Spigelman also said the inclusion of ''religion'' as a protected attribute in the legislation appeared to make blasphemy unlawful at work, but not elsewhere. This meant the Danish cartoons - featuring Muhammad - could be published, but not taken to work.

He said while the four existing acts proscribed publication of an advertisement or notice that indicated an intention to engage in discriminatory conduct, the new omnibus bill went further, by extending this to any publication.

It ''proposes a significant redrawing of the line between permissible and unlawful speech''. This was despite the ability to establish that conduct fell within a statutory exception. A freedom where something had to be proved after the event was ''a much reduced freedom''. Also ''the chilling effect of the mere possibility of legal processes will prevent speech that could have satisfied an exception''.

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