House MPs began examining a package of laws that would revise the country’s antitrust laws to curb the power of Amazon, Apple, Facebook and Google on Wednesday.

Later in the day, members of the House of Representatives Judiciary Committee are expected to vote on six bills that could prevent tech giants from prioritizing their own products online, forcing them to abandon parts of their deals and generating more resources for law enforcement agencies, monitor the Silicon Valley. Skeptical legislators can propose changes to the law or reject the measures entirely.

The committee took its first vote early that afternoon and voted for a bill that would increase the amounts of money companies pay to government agencies when some mergers are approved. That money could fund more aggressive antitrust enforcement, say its supporters.

The draft law passed the committee with 29 MPs for and 12 against. All Democrats present voted for the bill, with five Republicans joining them. Despite being considered one of the least controversial of the six measures, lawmakers still debated the law for hours and considered several proposed changes.

In the late afternoon, the committee tabled a second bill that would give attorneys general the power to try antitrust cases in courts of their choice. The bill – also one of the least controversial proposals supported by members of both parties and all attorneys general of states and territories – would prevent corporations from moving antitrust challenges to places they might consider more convenient for them. The vote was 34 to 7.

The Wednesday session is expected to last all day and possibly extend into early Thursday.

The bills tabled this month reflect growing concerns about the power of the biggest tech companies. The proposals, backed by members of both parties, unite Democrats concerned about runaway businesses with Republicans concerned about the power of online platforms to monitor online content.

“The digital market is suffering from a lack of competition,” said David Cicilline, Democrat of Rhode Island and chair of the Antitrust Subcommittee. “Amazon, Apple, Facebook and Google are the gatekeepers of the online economy.”

The proposals also have their share of critics.

Ohio Rep. Jim Jordan, the Republican chief on the Justice Committee, and Mark Meadows, former chief of staff to President Donald J. Trump, said in an opinion column on Fox News on Tuesday: Just wait for Apple, Amazon, Facebook and Google to join in Big Government work together. ”Some California Democrats are also concerned that the bills will put a brake on the state’s economic engine.

The tech giants have launched an aggressive campaign to block the bills. Tim Cook, Apple’s CEO, has called on members of Congress to express his concerns. Executives from other companies have spoken out against the bills in the past few days. And numerous corporate-funded groups have urged lawmakers to oppose the proposals.