Australia would have some of the toughest anti-piracy measures in the Western world if leaked government proposals to crack down on online copyright infringement were implemented, according to copyright experts.

The draft discussion paper, published by news site Crikey on Friday, includes proposals to block overseas websites that host pirated content and to compel internet service providers (ISPs) to stop users illegally downloading movies and music.

Attorney-General George Brandis has said Australia - which topped the world for illegal downloads of Game of Thrones last year - is the ''worst offender'' when it comes to pirated content.

The paper proposes to make it easier for content creators to take ISPs to court if they don't implement action against illegal downloading and to force ISPs to block access to sites hosting pirated content.

The proposals would overrule a 2012 High Court decision that found ISPs such as iiNet, Telstra and Optus cannot be found liable for authorising an act by a subscriber infringing copyright.