A woman who cleaned her house topless has been charged with a crime that could see her having to register as a sex offender in the US.

Tilli Buchanan, 28, was working alongside her husband in the garage of their Utah home in late 2017 or early 2018 when they both removed their shirts to prevent dust from getting on them, AP reports.

Buchanan's stepchildren, aged 9 and 13, saw the couple both topless — and when their birth mother later heard about the incident, she told child welfare officials because she was "alarmed".

The stepmother has been charged with three counts of misdemeanour lewdness involving a child.

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Her husband faces no charges.

If convicted, she could be forced to register as a sex offender for 10 years.

"If we lose this, she's on the sex offender registry with child rapists and things of that nature," her lawyer, Randy Richards, told the Salt Lake Tribune.

"The magnitude of the penalty on this is enormous."

The stepmother is now fighting the case.

"It was in the privacy of my own home. My husband was right next to me in the same exact manner that I was, and he's not being prosecuted," she said.

Prosecutors in West Valley City argued she was "under the influence of alcohol" when she removed her shirt and made a comment that she would put it back on only if her husband exposed himself, local media reports.