The Republican bill to repeal and replace Obamacare hits older Americans who struggle financially the hardest, said AARP Legislative Counsel and Policy Director David Certner.
"The older you get and the lower your income, the bigger the premium increase you're going to see," Certner told CNBC's "Squawk on the Street" on Monday, the day the Congressional Budget Office could release its cost analysis of the GOP's American Health Care Act.
The CBO will put "clear numbers" on the AARP's concerns, he said. "I don't think you can argue with the math here. It doesn't matter if you have more choices if they're all unaffordable."
"Not only are insurance companies allowed to charge people more, the amount of tax credits available to seniors are going to go down," Certner said. "So there's a double-whammy."
Instead of Obamacare subsidies, the AHCA from Republicans would issue a tax credit to customers of individual health plans, with the value of that credit tied to age and income.
"What we're seeing here between age ratings and loss of tax credit is what we call a huge 'age tax,'" he said.
Certner countered assertions by the GOP that Obamacare is failing and going to collapse.
"We all know we can make changes to improve Obamacare," he add, saying he sees nothing in the GOP bill to bring premiums down. "In fact, for our folks [seniors] we see huge price spikes."
The AHCA does keep two popular provisions of Obamacare: the protections for people with pre-existing conditions and the ability for parents to cover their children under the age of 26.
While Obamacare taxed people for not getting coverage, the GOP plan allows insurers to charge a 30 percent penalty to consumers who had coverage and dropped it and then want it again.