A Liberal MP has warned the racism and ignorance embodied by One Nation leader Pauline Hanson could have tragic consequences for Australia, calling on his fellow politicians to explicitly reject her views.

Senator Hanson's incendiary first speech in the upper house on Wednesday - in which she said Australia was in danger of being "swamped" by Muslims, called for a ban on further Muslim migration and declared multiculturalism had failed - sparked widespread condemnation.

But while a number of Turnbull government MPs said they thought Senator Hanson's views were wrong, most were treading carefully given the Coalition needs One Nation's votes to help pass its legislation.

However in an impassioned speech in Canberra, John Alexander - the member for the heavily multicultural Sydney seat of Bennelong - has gone much further, calling Senator Hanson's speech "abhorrent".