Lies are creeping into about a fifth of marriages, according to a new survey conducted by the UK law firm Slater and Gordon.

The poll finds that 20 percent of respondents say they are keeping "a major secret" from their husband or wife. Of those, one in four admit that their lie is so significant, they fear its being exposed would end their marriage. Another quarter say they've been carrying the secret more than 25 years without their spouse finding out.

Almost 30 percent believe that coming clean would only make things worse for them, and 12 percent say they've gone to extreme lengths to hide their dirty laundry.

[Metro Networks]