The federal government is warily weighing up a change to the definition of small business in its proposed workplace laws in order to get them through the Senate.
But Workplace Relations Minister Tony Burke warned increasing the definition of a small business from 15 to 20 workers - recommended by an inquiry report into the bill - would be a significant change.
Independent senators David Pocock and Jacqui Lambie, and the 12 Greens senators, are key to the bill passing in the last parliamentary sitting period for the year.
Senator Pocock says he supports 85 to 90 per cent of the bill, but wants time to consider the impacts of its more complex aspects such as multi-employer bargaining.
Mr Burke said the government was considering the small business change as part of its negotiations.
"If the government does accept that recommendation (from 15 to 20 workers) it means 97.5 per cent of businesses are excluded from that stream - 2.5 million businesses would be excluded from that stream," Mr Burke told parliament on Wednesday.
"That's a pretty big difference. That's a pretty significant difference."
Deputy Liberal leader Sussan Ley has hit out at the changes, saying small businesses would still be worse off under the reforms.
"(The report) did make that modest change, lifting 15 to 20, but that's not going to make a difference," she told Sky News.
"We know that the effect this is going to have on small businesses is incredibly bad."
Concerns have also been raised about the impact on airlines, with a Qantas submission to the Senate inquiry arguing it would drive up flight costs, particularly along marginal routes.
Neither Transport Minster Catherine King nor Mr Burke ruled out the possibility of the legislation impacting regional flights, but Mr Burke said workers deserved to see a share of corporate profits.
"It's not outrageous for the Australian workforce to see profits, to see businesses in Australia doing well, and wondering why they were constantly falling behind," Mr Burke said in parliament.
"I want more Australians to be able to afford to get on a plane."
On Wednesday, Qantas upgraded its half-yearly profit expectations by $150 million, with pent-up travel demand helping the airline turn its fortunes around.
The Labor government's estimates for the cost of the bill on business have also been questioned.
Government predictions have Australian small businesses footing a $14,638 bill to negotiate with employees under the low-paid bargaining stream, but the Australian Chamber of Commerce and Industry's best guess puts this upwards of $20,000.
"Even under its own methodology, the government has vastly underestimated the direct costs to business of being dragged into multi-enterprise negotiations, let alone the costs of being forced to work under unsuitable arrangements determined in union offices," ACCI chief executive Andrew McKellar said.
The government argues the bill would help get stagnant wages moving faster.
However, the debate on the bill comes as Reserve Bank governor Philip Lowe warned during a speech on Tuesday that increasing wages to match rapidly rising inflation could have a negative impact.
"If we all buy into the idea that wages have to go up to compensate people for inflation it will be painful, so best avoid that," he said.
Cabinet minister Bill Shorten said the problems was wages were stagnant.
"Where you've got inflation going up 7.5 per cent and wages aren't moving at all, that's a 7.5 per cent wage cut."
