A U.S. court upheld last week a dentist's decision to fire his long-time assistant on grounds that the latter's attractive appearance was threatening the employer's marriage.

In a decision issued on Friday, the Iowa Supreme Court had affirmed that dentist James Knight was acting legally when he terminated the working contract of his dental aide Melissa Nelson, who had worked 10 years on the former's clinic.

Ms Nelson was booted out because of 'irresistible attraction' allegedly felt by her former boss, The Associated Press said in a report, citing the Iowa court ruling.

Court records also showed that Ms Knight and Ms Nelson were not having an affair prior to the incident and that the latter was not acting in a flirtatious manner towards her employer.

Regardless, the court sided with the Mr Knight's arguments that he was protecting his marriage, forcing him to ease out Ms Nelson, who the dentist described as competent on her job.

"Such firings may be unfair, but they are not unlawful discrimination under the Iowa Civil Rights Act because they are motivated by feelings and emotions," AP quoted the court decision as saying.

The court also appeared supportive of Mr Knight's claims that he chose to save his marriage in acting on Ms Nelson's termination, which the former admitted was partly prompted by the demands coming from his wife.

It is understood that the two, both married, exchanged text messages but stopped short of starting a relationship though Ms Nelson had testified before the court that her boss sometimes sent her messages that are sexually suggestive.

"Ms Nelson recalled one text she received from her boss asking: How often she experienced an orgasm?" AP said on its report.

Also, when allegedly confronted by Ms Nelson's husband, Mr Knight reportedly admitted that "he feared he would have an affair with her down the road if he did not fire her."

Clearly disappointed by the ruling, the dental assistant told U.S. network ABC News: "I think it is completely wrong ... I think it is sending a message that men can do whatever they want in the work force."

"I'm devastated. I really am," she added.

However, Mr Knight's lawyer, Stuart Cochrane, insisted that the all-male court handed down the correct decision, adding that his client was acting in the best interest of all the parties concerned.

"While there was really no fault on the part of Mrs. Nelson, it was just as clear the decision to terminate her was not related to the fact that she was a woman. The motives behind Dr. Knight terminating Mrs. Nelson were quite clear: He did so to preserve his marriage," Mr Cochrane told AP.

Ms Nelson's lawyer, Paige Fiedler, believed otherwise. "We are appalled by the Court's ruling and its failure to understand the nature of gender bias," Ms Fiedler wrote in a statement.

"Although people act for a variety of reasons, it is very common for women to be targeted for discrimination because of their sexual attractiveness or supposed lack of sexual attractiveness. That is discrimination based on sex," Ms Fiedler was quoted by ABC News as saying.