The latest dust-up over President Barack Obama’s health-care-for-all mission — the congressman who angrily called Obama a liar during a nationally televised speech — underscored conservatives’ fears that illegal immigrants would benefit from efforts to expand coverage. But if immigrant-rich California is any indication, there are already millions of undocumented immigrants on publicly funded health plans — and it comes at a cost to taxpayers.

While the vast majority of federal benefit programs bar those who cannot present proof of citizenship, California has been more generous than other states. Taxpayers here contribute more than $1 billion each year to cover the health care costs of those who are in the country illegally.

The California Department of Health Care Services estimates 768,400 undocumented immigrants will receive coverage this fiscal year through Medi-Cal, the health program funded by state and federal tax money. The cost: $1.2 billion. While people without documentation aren’t eligible for the full menu of comprehensive health care other low-income residents receive, those who show up at emergency rooms are covered.

Another state and federally funded program, Access for Infants and Mothers, serves pregnant women whose income is slightly higher than Medi-Cal eligibility allows. That program enrolls 12,000 women statewide at a cost of $123 million, according to the Legislative Analyst’s Office. Some participants are presumed to be undocumented, said Lisa Murawski of the analyst’s office, although no questions are asked.

According to the most recent estimates by the Public Policy Institute of California, there were 2.8 million illegal immigrants here in 2006 — one-quarter of the nation’s total.

Whether the public’s investment in health care for illegal immigrants is worth the expense remains the subject of debate.

Immigrant-rights advocates and public health officials argue that providing basic medical care to all prevents more costly emergency services and stems the spread of infectious disease. Critics assert that providing health benefits to illegal immigrants entices them into the country and squanders precious public dollars.

The president made clear in his address to Congress this week that he has no intention of making access for the undocumented any easier. “There are those who claim our reform efforts would insure illegal immigrants — this too is false,” Obama said, to which Rep. Joe Wilson, a South Carolina Republican, shouted: “You lie!”

Republican critics says the proposed legislation does not do enough to ensure government dollars won’t flow to those who are here illegally. Wilson said Thursday that GOP efforts to toughen the bill by requiring verification of citizenship were defeated by Democrats in Congress. Indeed in California, some programs ask, and some don’t. Emergency rooms here and across the country guarantee care because federal law bars hospitals from refusing service, regardless of immigration status or ability to pay.

The number of undocumented immigrants seeking care at emergency rooms is often difficult to tease out, because they aren’t tallied separately from other uninsured patients.