WASHINGTON — Democrats in Congress are trying to block companies from cutting their tax bills by moving their legal address outside the United States through a merger.

Companies are forging ahead anyway.

“We’re working on a lot of deals that have this element to it,” said Robert Profusek, head of the mergers and acquisitions group at Jones Day in New York. “Nobody’s said, ‘Stop the music.’ ”

Lawmakers upset about so-called inversions are pledging that any limits they pass will be retroactive to May 8. They haven’t attracted a single Republican supporter.

Fourteen companies have completed or announced such deals since Jan. 1, 2012. Investors are pressuring other companies such as Walgreen Co. to consider the idea, at a pace that hasn’t slowed since Sens. Carl Levin of Michigan and Ron Wyden of Oregon called for retroactive tax laws.

The proposed deal that piqued congressional interest this month was Pfizer’s bid to buy AstraZeneca, take advantage of the lower British tax rate and leave its top executives in New York. AstraZeneca rejected Pfizer’s offers, and Pfizer ended its bid Monday.

Democrats’ attempt to build momentum for limiting such deals hasn’t persuaded companies that congressional action is imminent or likely. Corporate executives, frustrated at Congress’ slow pace in revamping the U.S. tax code, say the interest of shareholders requires them to consider ways to lower their taxes – including inversions.

“The message out of Washington is confused and weak instead of strong and unified,” said Terry Haines, head of political analysis at New York-based research company ISI Group.

Levin’s retroactive bill would effectively prevent U.S. companies from completing inversion deals through the acquisition of smaller companies in other countries. The foreign company’s shareholders would need to own at least half of the combined company, up from 20 percent today.

Levin’s plan also would limit those companies’ ability to be treated as foreign for tax purposes while keeping top executives in the U.S.

Levin’s legislation, which would expire after two years to give Congress time to revise the rest of the tax code, would generate $791 million in revenue, according to the congressional Joint Committee on Taxation. The permanent companion House bill would raise $19.5 billion over 10 years.