The opposition's plans to scrap cash refunds for some shareholders and change negative gearing will provide crucial funding for their spending promises.

But crossbench parties including Clive Palmer's United Australia Party, Pauline Hanson's One Nation and Centre Alliance have signalled they could block tax reform in the upper house.

Opposition Leader Bill Shorten said his party would have a mandate for its tax reforms because the plans had been made public well in advance of the election.

"Let's not have three more years of minority parties controlling the Senate," he told reporters in Geelong.

"I do believe we will have a mandate and I'm a very determined person."

Labor's finance spokesman Jim Chalmers said it was no surprise Mr Palmer sided with the Liberals, given he would benefit from coalition policies.

"We'll put our changes out there, we'll argue for them, we'll have the necessary discussions, but we intend to pass the tax changes that we've proposed," the Labor frontbencher said.

He said Labor senators had discussed tax policies with crossbench colleagues since its agenda was released.

Australian Conservatives senator Cory Bernardi said Labor had not respected mandates from previous governments.

"I don't support tax changes of this nature," he told the ABC.

"This is just self-serving and quite frankly, a little hypocritical by Labor."

Senator Bernardi said while he wouldn't be an impediment for the sake of it, governments did not get a blank cheque to get legislation through the upper house.

But he can see Labor's agenda winning support in the Senate.

"I do see pathways because I've seen people in the Senate ditch their longest-held principles at the slightest whiff of political advantage," the SA senator said.

Treasurer Josh Frydenberg said voters would reject Labor's "high tax and spend agenda".

"Bill Shorten has a plan to weaken the economy, create fewer jobs and deliver lower wages, with $387 billion in higher taxes."

Australian Associated Press