Washington — Older workers headed toward retirement are some of the biggest losers under the GOP legislation to replace the Affordable Care Act.

By slashing their financial assistance for coverage, allowing insurers to charge them more and repealing taxes that boost Medicare’s shaky finances, the GOP bill poses a triple threat to the health and well-being of working adults ages 50 to 64.

When the health law was enacted in 2010, people in this age group were the fastest-growing group of uninsured in the country because many couldn’t get individual coverage due to pre-existing medical conditions, said David Certner, legislative policy director at AARP.

In the first two years after the Affordable Care Act was implemented, the uninsured rate for 50- to 64-year-olds fell 47 percent, AARP research found.

The Republican legislation puts that trend in dire jeopardy.

“This is a big comprehensive step back from some of the gains that we’ve made since the enactment of the Affordable Care Act,” Certner said.

Today, 6.1 million people ages 50 to 64 have individual insurance and 3.2 million are eligible for federal tax credits and subsidies to help pay for coverage.

The Republican measure would cut that financial assistance by $673 billion in 2020 by eliminating the subsidies and providing smaller tax credits based on age rather than income and costs.

The bill also would allow insurers to charge older people up to five times more for coverage than younger adults. Tax credits for older people, however, would be only twice as large as those for younger adults.

A study commissioned by AARP found that premiums for those 60 and over would jump an average of 22 percent, or $3,192, per year because of the higher prices.

Adults in their 50s would see an average 13 percent increase of about $1,524 per year.

With less financial help and higher costs, older people will be hit with a “double whammy,” Certner said: losing access to coverage and paying more for it under the Republican plan.