The mayor of Utah’s second-most-populous city made an unusual appearance Monday in a paid advertisement for EnergySolutions, touting the company as a safety-conscious disposal site for low-level radioactive waste and as a critical component of the state economy.

In a glowing testimonial published on the Utah section covers of The Salt Lake Tribune and Deseret News, West Valley City Mayor Mike Winder characterized EnergySolutions as “Utah’s most misunderstood company” and said its efforts to responsibly dispose of waste could benefit Utah and beyond.

But in doing so, did he step over an ethical line?

Winder, who used his title of mayor in the ad, oversees public affairs for a company that counts EnergySolutions as a marketing client — although his company wasn’t involved in “The Nuclear Renaissance” piece featuring him. He also received a campaign contribution from the company.

Winder insists that his endorsement of EnergySolutions was proper. He had an opinion. He expressed it. And he didn’t hide his relationship with the company.

The mayor disclosed in the first two paragraphs of the ad that he had sought a donation from EnergySolutions during his mayoral campaign last year and that he had helped the company with communications “in my professional capacity as a marketer.” He received no compensation for his testimonial.

“I was very clear in writing this where I was coming from,” he said.

But Michael Josephson, president of the Josephson Institute of Ethics in Los Angeles, described the advertisement as clearly unethical.

Under no circumstance should a public official use his office to “lend prestige or credibility to a private enterprise,” Josephson said. And under no circumstance should a public official participate in advertising that could profit him personally.

Winder, he said, appears to have a “clear, undisputed financial conflict of interest” because of his position as director of public affairs for the Summit Group, which does marketing work for EnergySolutions.

“It is not a tough case,” Josephson said. “We just have to expect better of our public officials.”

Josephson downplayed EnergySolutions’ contribution to Winder’s campaign as a potential ethical problem. Campaign finance rules, he said, are written to keep companies from exercising undue influence on public officials. EnergySolutions donated $500 to Winder’s mayoral bid, making it one of his top 10 contributors.

Kirk Jowers, director of the University of Utah’s Hinckley Institute of Politics, was less critical of Winder’s involvement in the advertisement. Part-time public officials are bound to encounter conflicts of interest with their private-sector lives. The question is how they deal with them.

“It is a fair question whether elected officials should be involved in any company’s advertising campaign,” he said. “But once you get past that hurdle, the fact that Mayor Winder disclosed his personal financial interest in the company would mitigate my ethical concerns.”

It is rare for an elected official to appear in advertising for a for-profit company.

Then-Lt. Gov. Olene Walker came under some fire for appearing in a full-page magazine ad for her family’s potato chip company in 1993, though the spot did not use her title. And two years ago, some eyebrows were raised when a company that had donated to Attorney General Mark Shurt- leff’s campaign posted on its website a letter from the elected official praising its data-sharing technology.

State ethics laws are silent about public officials endorsing private companies or products, though there is a general prohibition against explicitly using public office for private gain.

The EnergySolutions advertisement is part of a public-relations campaign that the nuclear services company hopes will improve its image through radio, television and print promotions.

“It is really about education,” said company spokesman Mark Walker. “It is about helping people better understand the role we play in the nuclear industry.”

Although the Summit Group has been involved with the company’s marketing efforts, most recently with radio and television commercials, the public-relations firm had no role in the newspaper advertisement that featured Winder. Walker said no other public officials are in the lineup for future ads.

Winder, who received no money from EnergySolutions for his testimonial, describes his participation as a matter of fighting for the underdog.

“I have stuck my neck out on a number of hot issues,” he said. “Nuclear waste is one them.

And nuclear issues certainly are hot in Utah, where controversy continues to swirl over proposals to dispose of depleted uranium and blended nuclear waste in the Clive landfill. EnergySolutions recently announced that it no longer will seek to import significant quantities of foreign radioactive waste into Utah and, instead, will export its expertise in helping nations build their own specialized landfills — a move Winder describes as “the beginning of a new era for EnergySolutions.”

Corey Rushton, a West Valley City council member, wishes Winder would have made it more clear that he was speaking individually and not for the city. He added, “I don’t have a lot of heartburn about it.”