As the March 31 enrollment deadline approaches, insurers are increasingly urging consumers to sign up for health plans under the Affordable Care Act, even as some take swipes at the law, according to a new analysis of health-care advertising.

Forty-six percent of insurer ad spending during the week of Feb. 24 went to commercials featuring the law, compared with 32 percent the week before, according to the ad tracking group Kantar Media CMAG.

The costly advertising blitz — averaging more than $10 million per week since the beginning of December — is probably raising the law’s profile, but it is unclear whether it will increase its favorability rating.

Elizabeth Wilner, a senior vice president at Kantar Media, said the ads “tilt in the direction of trying to leverage people’s concern and confusion to come directly to the insurer to sign up. . . . The ads are not necessarily helping public opinion improve about the law.”

Blue Cross and Blue Shield of North Carolina, for example, faults the law as it urges customers to come directly to them to enroll for coverage.

“Why are medical costs and health-insurance premiums still skyrocketing despite health-care reform?” the narrator asks in the ad, which has aired more than 150 times in six media markets across the state since mid-February. “Because the Affordable Care Act, while having good goals, wasn’t designed to tackle new costs. In fact, the law has added new taxes, fees and benefits that actually increase the cost of health insurance.”

Karen Ignagni, president of America’s Health Insurance Plans, a trade group, said industry ads will target young and healthy Americans who have procrastinated in signing up or may have been discouraged from enrollment during the program’s rocky rollout in the fall.

“What you’ll see this month is a very strong focus on messages to the younger and healthier individuals who may not be aware that open enrollment is ending,” she said in an interview. “We always knew the first people in would be the people in need of immediate health-care treatment and that the last people in would be the youngest and healthiest.”

Insurers are not the only group funding ads — the conservative group Americans for Prosperity has spent at least $27 million in an effort to undercut the health-care law, while the Centers for Medicare and Medicaid Services (CMS) is spending roughly $52 million on paid media to promote enrollment through between Jan. 1 and March 31.

CMS has sought to reach young people by airing television ads on networks such as ESPN and shows including “Family Guy,” “Revolution,” “Arrow” and “The Vampire Diaries,” while also buying ads during the Olympics and the first several rounds of the NCAA men’s Division I college basketball tournament.

The liberal advocacy group, meanwhile, recently announced it will spend at least $100,000 this month on mobile ads featuring a “tap to call” technology, in which a cellphone user can be connected with an enrollment specialist by simply touching an ad.

The ads do not always appear in the same venues. Insurers tend to advertise on national networks, Wilner said, while the more political ads appear more often on local cable channels.

But the insurer advertising is significant because companies have still outspent any other single group, according to Kantar Media, devoting roughly $75 million between Dec. 1 and Feb. 28.