Attorney-General George Brandis has hit out at criticism of Tony Abbott's religious beliefs, describing the "ridicule" to which the former prime minister was subjected as "bigotry at its most shameless".

Senator Brandis, who last year defended people's "right to be bigots" amid debate over proposed changes to the Racial Discrimination Act, has told a roundtable meeting of religious and non-religious representatives that "religious freedom is every bit as important as political freedom".

But Senator Brandis said "members of Christian faiths, in particularly Catholic faith, are routinely the subject of mockery and insult by prominent writers and commentators".