Labor will launch a blitz on Liberal-held marginal seats to warn migrant communities about the Abbott government's plans to water down race hate protections.

ALP sources said the grassroots campaign, already well advanced in its planning, would use a network of ethnic community groups and media outlets to disseminate information during the month-long consultation period announced by Attorney-General George Brandis on Tuesday.

Senator Brandis put his controversial changes to the Racial Discrimination Act before the Coalition joint party room before publicly launching an explanatory bill for consultation.