The Telstra move was reported by the Australian Financial Review.
Contacted for comment, Steve Carey, general manager media, Telstra Corporate Affairs, confirmed the boycott, saying:
"We have strict guidelines around our brand and advertising and we are working with Google to ensure these guidelines are upheld. In the meantime, we have made the decision to pause our advertising on YouTube until we are satisfied there is an appropriate level of protection for our brand."
Holden and Kia were also reported to have followed suit.
Confirming the Tourism Australia decision to iTWire, Leo Seaton, the organisation's general manager, media and communications, said: "Tourism Australia takes all matters of brand safety extremely seriously and we are in close and regular contact with Google — directly and through our media agency UM — to better understand this situation and any possible impacts it may have."
He added that Tourism Australia had minimal activity on the YouTube platform.
The boycott began in Britain after The Times reported that ads for the government and major brands were appearing next to content that pushed extremist, racist and anti-Semitic material.
Two weeks ago, the British arm of the French firm Havas SA withdrew ads for clients in the UK from YouTube and the Google Display Network.
And last week, American companies AT&T, Verizon, Starbucks and General Motors said they were pulling their ads from YouTube.