Is there a better way than the 401(k) to build retirement savings?

If you believe 401(k)s are a joke — many people will never save enough or invest well enough to retire — then perhaps the idea of a mandatory savings account might do the trick.

It's not an idea that's likely to spread like wildfire, given that a massive retirement crisis isn't going to erupt tomorrow. And 401(k) savers who rode the wave of the bull market, frankly, aren't complaining much these days.

Yet Hamilton "Tony" James, executive vice chairman of Blackstone, is pushing the notion of a new type of mandatory savings account based on a long-term worry.

"We're going to have huge numbers of the elderly poor," said James, who is the co-author with labor economist Teresa Ghilarducci of a new book called "Rescuing Retirement: A Plan to Guarantee Retirement Security for All Americans."

He said only about 15 percent of Americans have a defined-benefit pension plan. Among the rest, only half have a 401(k) plan and the other half have nothing, he said.

Millennials have a particularly tough time, he said, because they are burdened by student-loan debt and some don't start saving for retirement until well into their 30s.

People might not have retirement savings because they work for an employer who does not offer a 401(k) plan or a pension; some don't want to participate and save money in a 401(k) plan.

James first raised the idea of a national retirement savings plan in 2015, and the new book further drives home that point.

The plan is for a Guaranteed Retirement Account where workers and their employers would each contribute 1.5 percent of wages into the accounts. The plan would create a new $600 federal tax credit for all savers. As a result, a lower income saver would be able to save because their contribution would be offset by the credit itself.

The money would be managed by professionals, much like a pension plan and would not replace Social Security. The payouts at retirement would be based on a lifelong annuity for the retiree and spouse.

"It's your money. It's your account," James said.

James said people would be allowed to stay in the 401(k) or move to the guaranteed retirement account.