Opposition Leader Bill Shorten has laid down a challenge to Prime Minister Malcolm Turnbull, goading him hold a public debate over hiking the GST.
Mr Shorten wants to take on his counterpart at the National Press Club in Canberra, daring him to "turn up and put the case" for increasing the tax from 10 to 15 per cent.
"If Malcolm Turnbull's fair dinkum, he'll front up," he told reporters in Queanbeyan on Tuesday, confident he can prove the hike is a "bad idea".
Education Minister Simon Birmingham dubbed the opposition leader "grossly irresponsible" for ruling out changes to components of Australia's tax system.
The Turnbull government was taking a "mature and sensible" approach through its tax reform white paper which would analyse the entire system, he told reporters in Sydney.
