Barnaby and Malcolm having a 'great' trip

It might not be Thelma and Louise, but Malcolm Turnbull says he's having a great time touring Queensland with his new deputy prime minister.

Mr Turnbull is visiting Rockhampton on Tuesday with Barnaby Joyce, as part of a four-day visit to the state.

"It's not Thelma and Louise, it's Barnaby and Malcolm but we're on the road trip and we're having a great time," he told a gathering at Central Queensland University.

Opposition Leader Bill Shorten later joked about the prime minister's Hollywood reference, saying at least Thelma and Louise had a plan.

"It worries me that they don't understand what they are doing or where they are going and the consequences will be drastic for the Australian people," he told reporters in Adelaide.

Mr Shorten demanded Mr Turnbull categorically rule out a hike in the GST, despite the prime minister having indicated it wasn't his preferred option.

"It is time for Malcolm Turnbull to stop the waffle and say he will not have a 15 per cent GST," Mr Shorten said.