Treasurer Scott Morrison insists Australians will benefit from new laws aimed at protecting two million small businesses from bigger rivals.
But there's doubt as to whether they will get through the Senate.
Parliament's lower house passed the legislation on Tuesday, despite opposition from Labor and concerns from within the government.
The so-called "effects test" bill strengthens rules that prevent companies with substantial market power engaging in conduct that harms competition.
Mr Morrison says it represents one of the most significant reforms to competition laws in recent times.
It will ensure a level playing field in business, including for over two million small local companies.
"To the ultimate benefit of Australian consumers," Mr Morrison told MPs.
Liberal backbencher Craig Kelly criticised the changes during debate on Monday night, concerned it would make it harder to prove breaches of competition law.
"It will be a number of years until the courts determine the effect of this legislation and I hope that I'm wrong," he said.
While the Greens have been fighting for the law changes, the government's chances of getting the bill through the Senate may be in jeopardy.
The minor party has concerns about other parts of the legislation that remove existing mechanisms covering the telecommunications sector.
There are also concerns around penalties for secondary boycotts.