Considered by some to be even worse than physically cheating, about 20 percent of Americans are currently hiding a checking, savings or credit card account from their spouse or live-in partner, a new survey shows.

The national survey of 1,000 adults by CreditCards.com finds 29 million Americans are not being truthful with their lover regarding their finances — whether it's a massive amount of debt they're too embarrassed to reveal, or a nest egg they want no one else knowing about.

Another 5 million used to hide an account from their current romantic partner, but no longer do, the survey finds. The practice is more common among Millennials than older generations.

Marty Tashman, a marriage and family counselor, said hidden money issues are not uncommon among clients at his office in Somerset.

"As a general rule, the more transparency, the better," Tashman said. "It isn't the separate accounts that's the problem. What's the problem is the secrecy of it."

Finances as a whole, Tashman said, is a frequent and contentious topic among couples he sees. When one person is a spender and the other's a saver, he said, a couple will have more arguments about money than they do their sex life.

As a remedy, Tashman said, couples may agree to have an "amnesty period" during which each party can reveal any financial secrets without fear of judgement from the other side.

"If it's debt, then as a team we're going to figure out how to handle it," Tashman explained. "Because if a couple's married, certainly one person's credit affects another's."

In the survey, 55 percent of respondents said keeping a secret bank or credit card account is at least equal in severity to physical infidelity. Within this group, 1 in 5 said it's even worse.

But only 2 percent of those living with their partner said they'd end the relationship if they discovered $5,000 worth of hidden debt. More than 80 percent said they'd be upset but would stick it out.