The chief executive of the Australian Bankers' Association, Steven Munchenberg, warned the joint select committee on gambling reform that trying to restrict transactions was "not straightforward".
The committee is investigating a bill introduced by the independent Senator Nick Xenophon to restrict financial transactions on prohibited internet gambling sites.
"[If] Australia was identified as a jurisdiction where payment obligations may not be fulfilled in a certain and timely manner, it is possible that merchants and online service providers will refuse to accept business and payments from customers designated as originating from Australia," Mr Munchenberg said.
"This would have a significant impact on the contestability of Australian businesses as well as the ability for Australian consumers to purchase online goods and services."