"It has been estimated that those program lapses resulted in the delay or cancellation of more than 1,400 home closings per day, further damaging an already fragile housing market," the senators wrote.

The letter, led by Sens. Jon TesterJonathan (Jon) TesterOvernight Cybersecurity: Equifax security employee left after breach | Lawmakers float bill to reform warrantless surveillance | Intel leaders keeping collusion probe open Overnight Finance: White House requests B for disaster relief | Ex-Equifax chief grilled over stock sales | House panel approves B for border wall | Tax plan puts swing-state Republicans in tough spot Senators grill ex-Equifax CEO over stock sales MORE (D-Mont.) and David VitterDavid VitterYou're fired! Why it's time to ditch the Fed's community banker seat Overnight Energy: Trump set to propose sharp cuts to EPA, energy spending Former La. official tapped as lead offshore drilling regulator MORE (R-La.), also notes that while the House approved a long-term flood insurance program last July, the Senate has yet to move on a bill approved by the Senate Banking Committee.

The Property Casualty Insurers Association of America welcomed the letter and said it shows the Senate is ready to follow the House's lead.

"This strong, bipartisan support in the Senate underscores the sense of urgency for passing a long-term solution for the National Flood Insurance Program," said Ben McKay, senior vice president of federal government relations for PCI. "Millions of American home and business owners rely on flood insurance in every state. This is not just a coastal concern."

The House-passed bill would restructure the NFIP by phasing in actuarially sound flood insurance premiums, which supporters hope would would help erase the nearly $18 billion in debt that the program has racked up over the past several decades. In the final version passed by the House (which was part of the payroll tax extension bill), this change was expected to raise $4.9 billion over 10 years, allowing the program to start paying down this debt.

— This story was updated at 4:22 p.m. to reflect the final scoring of the House-passed flood insurance bill at $4.9 billion, not $4.2 billion.