Prime Minister Malcolm Turnbull says it is "inconceivable" any changes to the GST will be made without compensation.
When asked by Labor in parliament's question time on Monday whether the GST would be applied to childcare, Mr Turnbull acknowledged low-income families would be disadvantaged without compensation.
"This is why it would never be done, that is why it wasn't done in the past, that is why it's inconceivable," he said.
Mr Turnbull reminded shadow treasurer Chris Bowen the government has not proposed increasing the GST.
There were many proposals for tax reform being debated at the moment, he said.
He said the government needed to show it was not reforming for reform's sake, but that the changes would deliver stronger growth and greater opportunities and be fair.
"We have also got to demonstrate that we have listened to every view, that we have consulted widely, that we have not taken things off the table in some sort of panic response to feeble scare campaigns," Mr Turnbull said.
