WHEN VENERABLE anti-tobacco groups such as the American Cancer Society and cigarette makers such as Altria align in opposition to a policy, it’s got to be pretty bad, right? But, when it comes to whether health-insurance companies can charge higher premiums from smokers, the fact that these mortal enemies oppose the idea doesn’t mean policymakers should throw it out.

When President Obama’s 2010 health-care law kicks in next year, there will be only a few things for which insurance companies can charge you more — your age, your location and whether you smoke. Smokers could face premiums that are up to 50 percent higher than those of non-smokers. You’d think that anti-tobacco activists would cheer. In fact, The Post’s Sarah Kliff reports, they have aligned with tobacco companies who want to eliminate the provision. Smokers are disproportionately low-income, and public-health groups worry that their premiums would be so expensive that many would choose to buy no insurance at all. That means a high-risk population would forgo needed disease screening and treatment, not to mention access to smoking-cessation coverage. Younger, healthier smokers would be more likely to opt out than would older, sicker ones, which could even raise insurance costs for everyone else. The Institute for Health Policy Solutions calculates that a married couple of older, low-income smokers could face premiums that equal as much as 48 percent of their total income.

Yet, as the institute’s study also notes, there are also good reasons to charge smokers more. Their behavior makes them prone to serious illnesses that are expensive to treat. If they don’t pay for their smoking-related medical care, non-smokers would have to finance a big chunk of the cost for that treatment. It’s also possible, though not proven, that higher insurance premiums would encourage smokers to quit.

These reasons alone wouldn’t justify pricing a cohort of low-income Americans out of the health-insurance market. But policymakers don’t need to eliminate the rules entirely — only refine them. Between now and next year, that can happen at the state or federal level, and it should probably occur at both.

For example, the federal government has already proposed to grant smokers in group insurance plans relief from the surcharge if they participate in smoking-cessation programs. Federal policymakers should seek to broaden that to the individual market. At the same time, they should make clearer what cessation products and techniques the government will require insurance companies to cover.

Individual states, meanwhile, can adjust the size of the maximum surcharge within their borders in various ways, ensuring a lower financial barrier to coverage. Though doing so could result in some smokers paying premiums that aren’t quite high enough to reflect the health risks they are taking, they would still have to chip in more for their health-care costs, without driving them to give up on insurance.