Multinationals trading in Australia funnelled more than $30 billion to Singapore in one year to avoid tax, an investigator says.
Jason Ward was part of a coalition that sought Freedom of Information documents over corporate Australia's tax avoidance.
He says the documents revealed $31 billion made in Australia in one year was shuffled through Singapore by 10 major companies.
But the documents protected the names of the companies involved.
"Any information which could identify individual companies has been blocked out," he told the Seven Network's Sunday Night program.
"There has to be consequences for these companies, for what they're doing. It's not illegal but it's completely immoral."
One company was responsible for an $11 billion transfer from Australia to Singapore in one year, Mr Ward said.
A Senate inquiry into tax avoidance is expected to table its first report in the parliament on Monday.
It's understood the report will make more than a dozen recommendations, including that the Australian Tax Office be forced to disclose all avoidance settlements above a certain level, and that a name-and-shame register be created.
Labor Senator Sam Dastyari, who chaired the inquiry, said the system was "completely broken" and privacy provisions were allowing Australia's worst offenders to hide.
He said corporates were essentially selling products to themselves, through companies set up in Singapore, to keep their profits down.
"When you have a handful of multinational companies able to take Australian taxpayers for a ride, the system has to change," Senator Dastyari said.
