Big businesses must promise to pass tax cuts on to workers' wages if key cross bench senators are going to vote for the government's planned changes.
Pauline Hanson says she has not yet been convinced on the tax cuts, which are before the Senate this week.
"Have we heard that big businesses say they are actually going to increase wages?" she told Sky News on Tuesday.
When asked if a guarantee from businesses would help her to vote for the cuts, Senator Hanson said: "It would."
Derryn Hinch also says he wants to see a guarantee from businesses that they will pass on tax cuts to increase wages.
"I'm worried that too much of it is going to be used for share buybacks or dividends," he said.
Both senators said they were still negotiating with the government on the corporate tax changes.
ACTU secretary Sally McManus said unions don't support the cuts because they are "trickle down economics".
"So much of this money ends up in offshore bank accounts," she said.
But Ms McManus said the government could increase the minimum wage to ensure the tax cut is passed on.
"Why isn't Malcolm Turnbull going and saying to the Fair Work Commission 'We support an increase to the minimum wage and we'll have a company tax cut'?" she said.
Labor and the Greens oppose the cut in the corporate tax rate for all-sized businesses from 30 per cent to 25 per cent, but the government can get a win with crossbench support.