Senator and presidential hopeful Elizabeth Warren is drafting a bill that would ban "mega mergers" between the nation's largest companies as well as try to improve the bargaining power of short-term and temporary workers.

The forthcoming legislation, a collaborative effort with Rep. David Cicilline of the House antitrust subcommittee, would bar tie-ups including a company with over $40 billion in annual revenue or two companies each with at least $15 billion in annual revenue, according to a person familiar with the matter.

It would also grant gig workers the power to unionize, a potential landmark change for ride-hailing companies like Uber Technologies and Lyft, the person told CNBC. Bloomberg News first reported that Warren and Cicilline were working on the legislation.

The proposal would broaden antitrust law beyond the 40-year-old consumer welfare standard, the framework that has dictated antitrust policy in the U.S. for a generation. Under existing regulation, the federal government's antitrust policies assess mergers based on their potential to hurt American consumers with monopolistic prices or diminished quality.

Warren and Cicilline's legislation would, in addition, compel the government to also weigh potential impact on workers and entrepreneurs.

But early response to the proposal suggested not only that the Democrats would have a hard time convincing their Republican peers to support such a measure, but that debate would have to wait until after the impeachment process against President Donald Trump.

"The numbers she has — the $40 billion in sales, no mergers beyond that — what decade does she think we're living in?" asked Republican and longtime political activist Grover Norquist. "We're not living in a time in a time with small companies competing in the world. American leadership has larger companies. It's really an odd 1910 world view."