Millions of uninsured legal immigrants will remain without coverage unless lawmakers adjust longstanding Medicaid rules that delay them from subscribing to the program, a new report finds.

Without those changes, the report's authors add, legal immigrants could continue contributing to the rising costs of healthcare across the country.

Roughly 3.4 million legal immigrants are currently without health insurance, a sizable portion of whom are between 150 percent and 400 percent of the federal poverty level, the Migration Policy Institute (MPI) indicates in its latest study, released Monday. But much of that demographic lacks access to Medicaid because the federal government already bars it from subscribing for at least five years, they explained.

That delay, which is preserved in every healthcare reform bill Congress is considering, means a number of immigrants could still head to their emergency rooms for primary care or otherwise lack access to preventive medicine — two key points in the healthcare debate that proponents stress would drive down costs for all, according to the report.

"Leaving large numbers of legal immigrants out of healthcare reform would defeat the core goal of the legislation, which is to extend coverage to the nation's 46 million uninsured," said MPI Senior Vice President Michael Fix. 

"The budget projections for healthcare reform assume substantial savings by excluding many immigrants, but do not factor in the costs associated with leaving so many people uninsured," added senior policy analyst Randy Capps. "Denying coverage does not eliminate the need for healthcare, and uninsured immigrants will head to emergency rooms or may postpone necessary medical attention — ultimately shifting costs to taxpayers and other health consumers."