LONDON (AP) — Royal Dutch Shell violated industry rules by claiming in a newspaper ad that two oil projects in Canada and the United States involved sustainable forms of energy, Britain's advertising watchdog ruled yesterday.

The Advertising Standards Authority investigated the Shell ad after a complaint from the World Wildlife Federation.

The advertisement focused on two of Shell's projects. One involves exploration in Canada's oil sands where bitumen, a tar-like form of petroleum, can be extracted and upgraded to synthetic crude oil. The ad also mentioned Shell's plan to build one of the United States' largest oil refineries in Texas.

"The challenge of the 21st century is to meet the growing need for energy in ways that are not only profitable but sustainable," said Shell's full-page ad in the Financial Times.

The watchdog ruled that Shell breached regulations relating to substantiation, truthfulness and that the advertisement "was defined primarily in environmental terms".

Shell argued that it also used "sustainable" to refer to the social and economic impact of the projects.

"It was never our intention to be misleading in our advertisement," said Sarah Smallhorn, a spokeswoman for Shell in London.

The authority also rejected Shell's argument that the design of the refinery at Port Arthur, Texas, would lower most types of emissions on a per barrel basis.

Citing a 2006 report by Canada's National Energy Board, the watchdog said the report claimed that the environmental impact of the country's oil sands projects were of major concern. Producing crude from bitumen can involve strip mining and generate more emissions than conventional crude.