A federal lawsuit brought by current and former members of Congress could result in lawmakers receiving hundreds of thousands of dollars each in back pay, along with significant future salary increases, if they ultimately prevail in court. The case could leave taxpayers responsible for at least $69 million in retroactive compensation, with even greater long-term costs if congressional pensions are also increased.

The lawsuit gained significant momentum last month after a federal judge ruled that the case may proceed, marking a major legal victory for the lawmakers seeking higher compensation.

The plaintiffs argue that Congress violated the 27th Amendment by repeatedly blocking automatic cost-of-living adjustments established under a 1989 law. According to their claim, lawmakers unlawfully prevented salary increases that were intended to keep congressional pay aligned with inflation.

If the courts ultimately agree with that argument, the National Taxpayers Union estimates that taxpayers would be responsible for paying at least $69 million in retroactive compensation to current and former members of Congress.

For nearly two decades, members of Congress have left their annual salary unchanged at $174,000, largely to avoid criticism over voting themselves raises. Privately, however, many lawmakers have expressed frustration that congressional pay has remained frozen while inflation has continued to rise.

“Seventeen years, I have gotten people from my side and people from the other side saying, ‘Can’t we fix this?’” Rep. Steny Hoyer (D-Md.), a former House majority leader and one of the plaintiffs in the lawsuit, said during an appropriations hearing last month.

“Our goal is to stop the continual violations of the Constitution as it relates to Congressional pay,” Ken Cuccinelli, the attorney for the suing lawmakers, told The Post in an email. “As a policy matter, I would note that Congressional pay on an inflation-adjusted basis is the lowest it has been since 1954.”

Cuccinelli, who previously served as Virginia’s attorney general and later as acting deputy secretary of the Department of Homeland Security during President Donald Trump’s first administration, assembled the class-action lawsuit on behalf of a bipartisan group of lawmakers. The named plaintiffs include Reps. Steny Hoyer (D-Md.), Rick Crawford (R-Ark.), James Clyburn (D-S.C.), and former Reps. Rodney Davis (R-Ill.) and Ed Perlmutter (D-Colo.).

Exactly how many current and former lawmakers could ultimately qualify for back pay remains unresolved. Federal Claims Court Judge Eric Bruggink has instructed both sides to address that issue in additional filings due later this summer.

Another unresolved question is the amount of damages that individual lawmakers could receive. Current estimates place potential awards at between $225,000 and $420,000 per member.

Beyond retroactive payments, a favorable court ruling could also restore automatic annual cost-of-living adjustments for members of Congress.

Under current estimates, congressional salaries could eventually climb to more than $253,000 annually—roughly 45% higher than today’s pay.

The financial impact could extend even further. Former members of Congress who receive higher salary calculations could seek increased pension benefits from the Office of Personnel Management, adding additional costs for taxpayers.

Demian Brady, vice president of research at the National Taxpayers Union Foundation, argued that if lawmakers believe they deserve higher salaries, they should pursue them through legislation rather than litigation.

“Because of all these perplexing questions, and because the damages will fall on taxpayers through higher deficit spending and potentially higher long-term liabilities, and also because of the reputational harm this will do to Congress as an institution, I’ve urged the lawmakers to drop their case,” he said.

“They should seek higher pay by convincing their colleagues to vote for higher pay instead of suing taxpayers.”

Those who support higher congressional salaries argue that members face substantial financial demands while serving in office, including maintaining one residence in their home district and another in Washington, D.C., one of the nation’s most expensive housing markets.

Congress last received a salary adjustment in 2009, when lawmakers’ annual pay increased 2.8%, from $169,300 to the current $174,000.

Since the ratification of the 27th Amendment in 1992, Congress has voted 21 times to reject automatic pay increases that otherwise would have taken effect.

The plaintiffs contend those repeated votes violate the Constitution’s 27th Amendment, which provides that no law “varying” congressional compensation “shall take effect, until an election of Representatives shall have intervened.”

In allowing the case to move forward, Judge Bruggink wrote, “Laws varying congressional compensation are ineffective to the extent they seek to effectuate a change in congressional compensation before an election intervenes.”