In a New York Times op-ed, Icahn warns that if action isn’t taken soon, we can expect more U.S. companies to follow the lead of the recent Allergan-Pfizer merger. The deal, which he notes as the largest inversion ever, moves a big U.S.-based drug company to Ireland to reduce its tax bill. Icahn claims to have spoken to many CEOs who have confirmed plans to follow in Pfizer’s footsteps.

The billionaire investor writes that the U.S. is “one of the few countries in the world” that requires an “antiquated double tax” on foreign earnings, which is currently set at 35%. He adds that our “uncompetitive tax code” is to blame for corporations hoarding foreign earnings overseas, which has added up to about $2.6 trillion, and it’s the reason why they eventually opt for corporate inversions.

Icahn believes a framework for international tax reform with bipartisan support composed by Senators Chuck Schumer of New York and Rob Portman of Ohio will fix this issue. It proposes a reduced tax rate of 8% to 10% for repatriation of foreign earnings. If the $2.6 trillion were brought back into the U.S., he says, we would see $200 billion in tax revenue and companies could invest the remaining earnings within the country, potentially creating thousands of jobs.

Congressional leaders appear to agree that passing this legislation would prevent inversions, but they’re still not taking action. As Icahn sees it, “too many politicians (and members of the press) don’t understand that there is a significant difference between ‘international tax reform’ and ‘comprehensive tax reform.'”

While there’s no consensus about comprehensive tax reform, which would address both domestic and international tax codes, there is bipartisan consensus that the Schumer-Portman framework could work.

Icahn references an interview with Pfizer chief executive Ian Read in which he suggests that the inversion could have been prevented. Read said that the U.S. tax code is “hugely disadvantageous to American high-tech multinational companies,” adding that he has been “totally unsuccessful” in bringing this issue to the forefront as something that needs to be resolved.

Icahn ends his op-ed by saying that CEOs have a duty to shareholders to enhance the company’s value.

The fault does not lie with them but with our uncompetitive international tax code and with our dysfunctional Congress for not changing it. How will representatives and senators, with an election year approaching, explain to their constituents why they are out of work because their employers left the country, when it could so easily have been avoided?