Greenpeace says a billboard they wanted to put up in downtown Edmonton was rejected without reason by Pattison Outdoor Advertising.

The environmental group had been in talks since early June to put up the billboard with the message: "When there's a huge solar energy spill, it's just called a nice day. Green jobs, not more oil spills."

The advocacy group wanted to put it at 106th Street and Jasper Avenue. However, the ad was rejected in an email which stated "unfortunately, we do not have approval to proceed with the artwork."

"Since then we made repeated email and phone attempts to try to get some reasons as to why but we haven't received anything back," said Greenpeace spokesman Mike Hudema.

Greenpeace spokesman Mike Hudema says his organization has had no success finding out why Pattison rejected the billboard. (CBC)

CBC News contacted Pattison Outdoor Advertising to find out why. The company emailed CBC back saying their official statement is "no comment."

Hudema says the company's position is unfair as it puts up billboards for oil and gas companies but won't let Greenpeace have its say.

"We see hundreds of billboards by CAPP, the Canadian Association of Petroleum Producers, running right across the country talking about how tailings are just like yogurt, and yet when you try to put up an ad in Alberta talking about the threats of oil spills, and the potential benefits of green jobs and renewable energy, that ad gets rejected," he said.

Adam Finn, a marketing professor at the University of Alberta, believes Pattison may have decided the Greenpeace ad would have offended some of their existing big clients, and it wasn't worth losing that revenue.

"The small risk that some of their important clients will be annoyed is way more important than the money they can get from this type of advertising," he said.

Instead, he says Greenpeace is running a successful public relations campaign when the media picks up the story