"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 ScottA guide to the committees: House Repeal without replacement: A bad strategy for kids House Dems press Trump for details on ObamaCare order MORE (Va.), Kathy Castor (Fla.), Earl BlumenauerEarl BlumenauerKentucky Dem lawmaker questions Trump's mental health A guide to the committees: House Democrats raise questions about Trump’s mental health MORE (Ore.), Mel Watt (N.C.), Bill Pascrell (N.J.), Elijah Cummings (Md.), Al GreenAl GreenA guide to the committees: House CBC to Trump: Keep Richard Cordray, ensure the protection of American consumers WHIP LIST: More than 60 Dems boycotting Trump's inauguration 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-LeeA guide to the committees: House House passes bill to roll back restrictions on unemployment drug testing Black Caucus Dems take to Senate to protest Sessions MORE (Texas), Judy Chu (Calif.), Robert Brady (Pa.), Charles Rangel (N.Y.), Gene GreenGene GreenA guide to the committees: House Overnight Healthcare: Trump officials weigh fate of birth control mandate | House, DOJ seek delay in ObamaCare lawsuit Top lawmakers from both parties: 'Vaccines save lives' MORE (Texas), Rosa DeLauro (Conn.), Marcia FudgeMarcia FudgeIf Democrats want to take back the White House start now A guide to the committees: House Dems claim unity, but are still in search of a message 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 YarmuthKentucky Dem lawmaker questions Trump's mental health A guide to the committees: House House Dems press Trump for details on ObamaCare order MORE (Ky.), Karen BassKaren BassA guide to the committees: House House Dems: Force Flynn to testify before Foreign Affairs panel CBC to Trump: Keep Richard Cordray, ensure the protection of American consumers 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 WelchBuyer beware: Not all 'milk' is created equal A guide to the committees: House Got soy milk? Don't let Congress, dairy industry bogart 'milk' label 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 BonamiciA guide to the committees: House Liberal Dems warn against narrow focus on rural or coastal voters 'Will on the Hill' pokes fun at 2016 election MORE (Ore.), John GaramendiJohn GaramendiA guide to the committees: House Outdated infrastructure poses national security risk Dems urge treaty ratification after South China Sea ruling 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.