They argued that the commission should still fight against media consolidation even though many consumers are now getting their news online.
"Simply put, resting any justification to relax the Commission's media ownership rule on the growth of Internet news ignores the millions of Americans not yet online," they wrote.
The letter carries particular weight because the Energy and Commerce Committee has jurisdiction over the FCC.
Sens. Bernie Sanders (I-Vt.), Maria Cantwell (D-Wash.) and Frank Lautenberg (D-N.J.) have also criticized the FCC's media ownership proposal, and 44 House Democrats sent a letter last week opposing the proposed changes.
Genachowski circulated a proposal with his fellow commissioners last month that would relax regulations that prohibit a single company from owning a TV broadcast station and a newspaper in the same market. The order would eliminate bans on newspaper-radio and TV-radio cross-ownership.
The FCC said last week that it would accept more comments on the proposal, postponing a vote until at least January.
In a statement issued earlier this month, Bill Lake, chief of the FCC Media Bureau, argued that the proposal "would strengthen the current rule by creating an express presumption against a waiver of the cross-ownership ban to allow such a combination."
"In addition, the proposed order preserves the existing TV duopoly rule, which forbids ownership of more than one of the top four TV stations in any market,” he said.
Some media and newspaper groups support the changes, arguing that the current regulations are hurting a struggling industry.
"This outdated rule prevents broadcast companies from investing in newspapers at a time when local journalism needs to be bolstered. It is time for the FCC to provide much-needed relief to the newspaper industry, which has labored under this ownership ban for far too many years," Caroline Little, president of the Newspaper Association of America, wrote in an op-ed
on Thursday in The Washington Post