"Even though we have made great progress addressing long-term rising health care costs with the passage of the Affordable Health Care Act, and even though the eligibility age for Social Security benefits is gradually increasing, it will do great harm to our economy and millions of seniors to raise the Medicare eligibility age or enact other significant cost-shifting alternatives," the lawmakers wrote.
House Minority Leader Nancy Pelosi (D-Calif.) was more pointed in her weekly press conference.
"Don't even think about raising the Medicare age," she said Thursday.
"We are not throwing America's seniors over the cliff to give a tax cut to the wealthiest people in America. We have clarity on that."
Proponents of raising the Medicare age from 65 to 67 say it is appropriate, giving rising life expectancy and the rapidly aging U.S. population.
Opponents argue it would raise premiums for Medicare beneficiaries and not save the federal government much money.
Thursday's letter came from, among others, Democratic Reps. Lloyd Doggett (Texas), Joe Courtney (Conn.), John Larson (Conn.), Louise Slaughter (N.Y.), John Lewis (Ga.), Jan Schakowsky (Ill.), Allyson Schwartz (Pa.), Raúl Grijalva (Ariz.), Frank Pallone (N.J.), Barney Frank (Mass.), John Tierney (Mass.), Danny Davis (Ill.), Henry Waxman (Calif.), Bobby ScottBobby ScottThe Hill's 12:30 Report House Dems may challenge Electoral College certification Dems press Trump to keep Obama overtime rule MORE (Va.), Kathy Castor (Fla.), Earl BlumenauerEarl BlumenauerDem boycotts of inauguration grow WHIP LIST: 54 Dems boycotting Trump's inauguration Pamela Anderson, Mary Matalin to co-host PETA inaugural ball MORE (Ore.), Mel Watt (N.C.), Bill Pascrell (N.J.), Elijah Cummings (Md.), Al GreenAl GreenWHIP LIST: 54 Dems boycotting Trump's inauguration Obama promises not to twerk at WH concert Dem lawmakers rally Muslims against Trump MORE (Texas), Janice Hahn (Calif.), Jim McDermottJim McDermottDem lawmaker: Israel's accusations start of 'war on the American government' Dem to Trump on House floor: ‘Stop tweeting’ A record number of Indian Americans have been elected to Congress MORE (Wash.), Sheila Jackson LeeSheila Jackson-LeePamela Anderson, Mary Matalin to co-host PETA inaugural ball Dems try to voice objections as Congress certifies Trump's win GOP lawmaker removes painting depicting police as pigs MORE (Texas), Judy Chu (Calif.), Robert Brady (Pa.), Charles Rangel (N.Y.), Gene GreenGene GreenLawmakers worry ObamaCare fight could suck air from other priorities Midwest Dems feel left out in cold Overnight Healthcare: Hospitals plot attack against ObamaCare repeal MORE (Texas), Rosa DeLauro (Conn.), Marcia FudgeMarcia FudgeWHIP LIST: 54 Dems boycotting Trump's inauguration Black Dems rip 'discriminatory' Sessions as unqualified for AG job Democrats take sides in race for DNC chair MORE (Ohio), Corrine BrownCorrine BrownDemocrats offer double-talk on Veterans Affairs House Democrats have opportunity for redemption in selecting VA Cmte Leader Women make little gains in new Congress MORE (Fla.), Eddie Bernice Johnson (Texas), John YarmuthJohn YarmuthWHIP LIST: 54 Dems boycotting Trump's inauguration House Dems call on OMB to analyze Senate budget plan Congress to clear path for Mattis MORE (Ky.), Karen BassKaren BassDem rep to skip inauguration after running Twitter poll WHIP LIST: 54 Dems boycotting Trump's inauguration La. rep picked to lead Congressional Black Caucus MORE (Calif.), Brad Miller (N.C.), Peter DeFazio (Ore.), Mike Honda (Calif.), Ted Deutch (Fla.), Yvette Clarke (N.Y.), Sam FarrSam FarrDEA decision against reclassifying marijuana ignores public opinion 19 House Democrats' sites hacked at close of gun sit-in Dems push for allowing base closures MORE (Calif.), Jose Serrano (N.Y.), Bennie Thompson (Miss.), Alcee Hastings (Fla.), Jim Langevin (R.I.), Keith Ellison (Minn.), Rush Holt (N.J.), Paul Tonko (N.Y.), Tim BishopTim BishopDems separated by 29 votes in NY House primary Flint residents hire first K Street firm House moves to vote on .1T package; backup plan in place MORE (N.Y.), Peter WelchPeter WelchOvernight Tech: Trump meets with AT&T, Google execs | Pompeo and Wyden battle | Dem's new House E&C roster Overnight Tech: Trump meets AT&T, Google execs | CIA nominee grilled on privacy | Court revives lawsuit over Apple apps | Trump team takes credit for Amazon jobs Oversight panel demands answers on Pentagon waste report MORE (Vt.), Bill Keating (Mass.), Chellie Pingree (Maine), Colleen Hanabusa (Hawaii), Jim McGovern (Mass.), Jerrold Nadler (N.Y.), Steve Cohen (Tenn.), John Sarbanes (Md.), Linda Sanchez (Calif.), Doris Matsui (Calif.), Carolyn Maloney (N.Y.), Emanuel Cleaver (Mo.), Suzanne BonamiciSuzanne BonamiciLiberal Dems warn against narrow focus on rural or coastal voters 'Will on the Hill' pokes fun at 2016 election Overnight Energy: Greens take aim at trade deals MORE (Ore.), John GaramendiJohn GaramendiOutdated infrastructure poses national security risk Dems urge treaty ratification after South China Sea ruling Fight over California drought heats up in Congress MORE (Calif.), David Cicilline (R.I.), Donald Payne (N.J.), Jackie Speier (Calif.), Maxine Waters (Calif.), Kerry BentivolioKerry BentivolioIndiana Republican: Leaders duped me Reindeer farmer saves 'cromnibus' with yes vote High drama as .1T spending package advances by one vote MORE (Mich.), Lynn Woolsey (Calif.), Russ Carnahan (Mo.), Maurice Hinchey (N.Y.), John Olver (Mass.) and Betty Sutton (Ohio) and Del. Eleanor Holmes Norton (D-D.C.).
—This post was updated at 4:05 p.m.