US Senator Elizabeth Warren has once again reiterated the need for more strict antitrust enforcement, backing efforts by Federal Trade Commission Chair Lina Khan and the Justice Department to overhaul the government’s guidelines for vetting mergers and acquisitions.

The so-called merger guidelines proposed by antitrust enforcers “are necessary at a time of rapid consolidation and inequality,” Warren and 21 other mostly Democrat lawmakers said in a letter Monday to FTC commissioners and Jonathan Kanter, who runs the DOJ’s antitrust division.

The letter urged the agencies to rapidly adopt the new guidelines and highlighted the need for enforcers to examine a broader range of deals, especially those that are part of a series of acquisitions made by a company within the same market, and to look at the impact on workers.

Warren has been a leading figure in the antitrust enforcement movement, arguing there was a need for more oversight and making it a core pillar of her 2020 re-election campaign to break up big companies.

Pro-business groups and conservative lawmakers have pushed back aggressively against the new merger rules.

But the lawmakers who support the changes said the guidelines are “grounded in law.” They also suggested some additional tweaks to “strengthen” the proposal, including a limit on the ability of companies to propose remedies to stave off scrutiny of their deals.

Warren and Representative Becca Balint, a Vermont Democrat, were the lead signers on the letter. Among the other lawmakers were Senators Mazie Hirono, a Democrat of Hawaii, and Bernie Sanders, an independent from Vermont, along with Representatives Barbara Lee and Katie Porter of California, Pramila Jayapal of Washington, Rashida Tlaib of Michigan, Cori Bush of Missouri and Jamaal Bowman of New York, all Democrats.

Read More: Merger Rules Get Tougher in Crackdown by Antitrust Enforcers

(Updates with lawmakers urging adoption of new merger rules.)