WASHINGTON — Hillary Rodham Clinton and Bernie Sanders are bashing plans by Pfizer and Allergen to join together in a $160 billion deal that will create the world's largest drugmaker.

The merger is a so-called inversion, in which U.S. companies looking to lower their tax bills combine with a company in a country with a lower tax rate. That merger potentially saves the U.S. company millions in U.S. taxes.

Clinton says that will leave "U.S. taxpayers holding the bag" and plans to propose steps to prevent inversions.

Sanders says the merger would be a "disaster" for U.S. consumers paying high prescription drug costs. He says the Obama administration should exercise its authority to stop the merger. Martin O'Malley calls the merger "fundamentally unfair."

Several U.S. drugmakers have performed inversions in recent years.