Mercer L.L.C. President and CEO Julio Portalatin is asking congressional leaders to roll back the sharp increases in insurance premiums employers will pay the Pension Benefit Guaranty Corp. as laid down by a new federal budget law.

These increases are not only unnecessary but are “counterproductive to the goals of enhancing the agency's financial health and improving Americans' retirement security,” Mr. Portalatin wrote in a letter sent Tuesday to Senate Majority Leader Mitch McConnell, R-Ky., Senate Minority Leader Harry Reid, D-Nev., Speaker of the House Paul Ryan, R-Wis., and House Minority Leader Nancy Pelosi, D-Calif.

Under the Bipartisan Budget Act of 2015, the PBGC flat rate premium — now $57 per plan participant and set to rise to $64 in 2016 under a prior law — will increase each year, starting in 2017 until it hits $80 in 2019.

In addition, the variable rate premium paid by employers with underfunded plans, set to rise next year to $30 per $1,000 of unfunded benefits from the current $29 rate, also will jump over a three-year period starting in 2017, until it hits $41 in 2019.

The latest premium increases, coming in the wake of “dramatic” increases lawmakers passed in 2012 and 2013, are “undermining employers' desire to maintain pension plans,” wrote the head of the New York-based benefits consulting firm.

“Unreasonably high PBGC premium are actually accelerating the decline of the very plans that the PBGC should be supporting and are thereby reducing the amount of premiums that will actually be collected by the agency,” Mr. Portalatin wrote.

As a consultant on retirement issues to more than 1,000 U.S. companies, Mercer knows “firsthand” how the earlier premium hikes are “undermining employers' desire to maintain pension plans,” Mr. Portalatin said.

Lawmakers, Mr. Portalatin wrote, should not only consider rolling back the premium hikes, but also should end a budget scoring practice in which premium increases can “look like revenue gains for the government even though they cannot, by law, be used for anything other than the PBGC insurance program.”