Medicare officials have failed to rein in Medicare Advantage overcharges despite decade-long crackdown

Government spending on Medicare Advantage , dominated by big health insurance companies, is expected to hit $462 billion this year .

The private insurance plans have morphed into a politically potent juggernaut that has signed up more than 33 million seniors and is aggressively lobbying to stave off cuts.

Critics have watched with alarm as the industry has managed to deflate or deflect financial penalties.

At least a dozen witnesses in the UnitedHealth case and a similar DOJ civil fraud case pending against Anthem are former ranking CMS officials who departed for jobs tied to the Medicare Advantage industry.

Marilyn Tavenner led the agency in 2014 when it backed off the overpayment regulation.

She left in 2015 to head industry trade group AHIP , where she made $4.5 million .

Sen. Elizabeth Warren and Rep. Pramila Jayapal have called for CMS to crack down on overpayments.

Advocates for Medicare Advantage plans worry that too much focus on payment issues could harm seniors.

The Better Medicare Alliance reported lobbying on 18 bills this year and last.