Australian shareholders are set to join a US class action against the National Australia Bank over the $A3.05 billion write-down of its Florida-based HomeSide Lending arm, which it sold last year. Slater & Gordon managing partner Andrew Grech said yesterday that his firm would join a US law firm in pursuing damages over losses estimated at up to $A750 million on behalf of NAB shareholders. Mr Grech said shareholders who bought NAB shares between April 1, 1999 and September 3, 2001, whether mum-and-dad retail investors or large institutionals, potentially had a claim.