Imperial Oil CEO John Whelan said the company supports a united Canada as Alberta prepares to vote on whether to begin the constitutional process toward a binding independence referendum, Bloomberg reported Tuesday, citing Whelan's comments at a Calgary conference.

Whelan said Canada and Alberta work best when people, products, energy and investment can move freely across the country, the report said. Imperial is the first major Alberta energy company to publicly take a firm position against separatism, Bloomberg said.

A provincial government-commissioned study found Alberta secession could reduce GDP by at least 2.2% over five years in a favorable scenario and more than 10% in a poor one, the report said.