Last Friday, ZDNet Australia revealed that banner adverts for both banks were appearing on The Pirate Bay Web site, which claims to be the world's largest BitTorrent tracker and potentially provides access to vast quantities of illegal content -- including music, films and games - as well as unlicensed software.
The banks initially denied they were advertising on the site but after being supplied with evidence to the contrary by ZDNet Australia, they launched immediate investigations.
On Friday afternoon, a St George spokesperson finally admitted that a "small number" of adverts were mistakenly placed on the Pirate Bay site.
"We are aware that a small number of adverts were placed with the site in question -- contrary to our established site selection criteria," said the spokesperson in an e-mailed statement. "St George has a strong policy of not advertising on any gambling, file sharing, adult or other 'controversial' sites."
According to the spokesperson, the adverts appeared on the Pirate Bay site because one of the bank's US-based media suppliers made a mistake while choosing appropriate target sites.
"An US-based organisation engaged by our media supplier did not manage the application of the site selection process appropriately and has apologised for their error," the spokesperson said.
According to a spokesperson from the NAB -- who thanked ZDNet Australia for alerting the bank about its rogue advert -- the banner was also sent to the Pirate Bay because of a mistake made by a third-party media buying firm.
"This has now been addressed. The advert should now be down -- if it is not, it will be soon," the spokesperson said.
The St George spokesperson said the bank had been offered "appropriate compensation" by its media buying partner. The NAB spokesperson was unsure if it would be compensated.