WASHINGTON — A large and growing share of American workers are tapping their retirement savings accounts for nonretirement needs, raising broad questions about the effectiveness of one of the most important savings vehicles for old age.

More than one in four American workers with 401(k) and other retirement savings accounts use them to pay current expenses, new data show. The withdrawals, cash-outs and loans drain nearly a quarter of the $293 billion that workers and employers deposit into the accounts each year, undermining already shaky retirement security for millions of Americans.

A report from the financial advisory firm HelloWallet found that more than one in four workers dip into retirement funds to pay their mortgages, credit card debt or other bills. Those in their 40s have been the most likely culprits — one-third are turning to such accounts for relief.

Fresh data from Vanguard, one of the nation’s largest 401(k) managers, show a 12 percent increase in the number of workers who took loans against their retirement accounts or withdrew money outright since 2008.

“What you have is 401(k) participants voting with their wallets saying they would much rather use this money for other purposes. I don’t think this can be ignored. Employers are dramatically overpaying for retirement, but it is not benefiting the employee,” said Matt Fellowes, a former Brookings Institution researcher who is chief executive of HelloWallet. “In many cases, the only one benefiting is the vendor.”

accounts as the primary vehicles for retirees to supplement their Social Security benefits.

Millions of Americans, caught between flat wages and high expenses for everything from sending children to college to making home repairs, feel as though they have little choice. The withdrawals have grown substantially in the wake of the financial crisis.

Charlotte Knox, 62, has worked as a housekeeper at Baltimore’s Hyatt Regency hotel since 1984. She earns $13 an hour, is struggling to recover from a hip replacement and is planning to retire next month. But partly because of past withdrawals, her 401(k) balance is only $60,000, which is all she has to supplement her Social Security.

“I don’t have any money,” she said. “I’m just taking it a day at a time. That’s all I can do.”

Fellowes said workers would be better served by establishing emergency savings accounts that steered clear of the potential tax penalties, investment fees, and other risks and costs associated with having money in retirement accounts.

Only after establishing an emergency savings fund, he said, should workers plow their money into retirement savings.