The ABC spends $2 million a year promoting its content on Google and Facebook in an increasingly fractious battle with commercial rivals for online audience.

Chief financial officer Louise Higgins revealed the broadcaster's annual expenditure on Facebook advertising was about $1.4 million, as well as the $500,000 it would spend boosting Google search results this year.

That was about half the ABC's annual marketing budget of $4 million, which Ms Higgins said was "a very small investment in making sure that Australians are aware of the content that we're making".

ABC chief financial officer Louise Higgins at Senate estimates on Wednesday night. Credit:Alex Ellinghausen

Last year the ABC spent $440,000 on Google keywords, Ms Higgins told a Senate committee. The increasing expenditure reflected the ABC's growing digital audience and the way Australians were consuming news and other content.