House Democrats, led by Speaker Nancy Pelosi of California, announced their plan to shore up the Affordable Care Act one day after the Trump administration told a court to strike down the entire law.
Democrats said changes in the ACA are needed to reverse what they called the administration's "sabotage" of the health care law.
The Department of Justice asked an appeals court to declare the ACA unconstitutional, siding with a lower court ruling issued in December.
The House plans to vote on the bill later this year, Pelosi said at a news conference. However, the bill has little chance of passing the Republican-controlled Senate.
The Democratic bill would expand the health care law's tax credits that help people pay for coverage. The proposal would help more middle-income families and individuals pay for health insurance, and would increase the size of the credits for everyone.
The measure aims to reduce premiums by helping insurance companies pay the claims of high-cost patients.
It also would prevent insurers from selling non-compliant plans expanded under the Trump administration. These plans are less expensive but have fewer benefits.
The bill would block the administration from approving requests from states looking to water down protections for people with pre-existing conditions as well as the ACA's requirements for covering what are called "essential health benefits," such as maternity care and substance abuse treatment.
The plan also comes as the progressive wing in the House pushes to scrap health insurance entirely in favor of Medicare For All. But House Democratic leadership has resisted Medicare For All, arguing that Congress instead needs to build up the ACA and defend it from Republicans and the Trump administration.