Dozens of Republicans – including ex-lawmakers and former party staffers – have signed a letter urging Republican National Committee Chairman Reince Priebus to “suspend” funding for Donald Trump’s campaign and divert all resources to congressional races, in the latest rebuke of the nominee from inside the party.

The letter, which is in draft form and expected to be sent next week, urges Priebus to focus RNC resources on saving the Republican majority in the House and Senate – effectively casting Trump’s campaign as a lost cause dragging congressional candidates down.

“Given the catastrophic impact that Donald Trump’s losing presidential campaign will have on down-ballot Senate and House races, we urge you to immediately suspend all discretionary RNC support for Trump and focus the entirety of the RNC’s available resources on preserving the GOP’s congressional majorities,” the letter says.

The letter, obtained by Fox News, cites a litany of complaints ranging from his controversial comments on the trail to his suggestion he might balk on NATO treaty obligations to his refusal to release his tax returns.

To date, however, Priebus has stuck by his public support for the nominee. He delivered a full-throated endorsement at last month’s Republican National Convention, where he declared: “With Donald Trump and Mike Pence, America is ready for a comeback after almost a decade of Clinton-Obama failures.”

The letter, signed by over 70 Republicans and first reported by Politico, is just the latest flare-up from Trump’s detractors inside the party.

Fifty former security and diplomatic officials from Republican administrations signed a letter earlier this week opposing Trump, while other prominent Republicans have either come out against him or gone a step further and endorsed Hillary Clinton. One of those figures was former Connecticut Rep. Chris Shays, who also signed the forthcoming letter.

Other co-signers include former New Hampshire Sen. Gordon Humphrey; former Missouri Rep. Tom Coleman; former RNC communications director B. Jay Cooper; and former RNC chief digital strategist Mindy Finn.

Trump has brushed off the intra-party tensions. After the security-official letter went public, he said those officials “are the ones the American people should look to for answers on why the world is a mess, and we thank them for coming forward so everyone in the country knows who deserves the blame for making the world such a dangerous place.”

Fox News’ Nick Kalman contributed to this report.