Unbridled oil sands expansion risks tarnishing Canada's global reputation, read briefing notes prepared for federal natural resources minister Joe Oliver.

"Rapid growth in oil sands production has led to increased attention being focussed on this sector, such that this issue has become a threat to Canada's international brand," warn the notes, which are marked "Secret".

The briefing document was obtained through an access to information request by Postmedia News. Its warning appears to have been addressed to Oliver sometime after he became natural resources minister in May 2011, but before the fall of that year.

"The environmental performance of oil sands development in Canada is under intense public scrutiny," the notes read.

Key concerns, they add, include "water contamination"; "inadequate" monitoring; the impact of tailings ponds; and rising greenhouse emissions, which are set to grow to 12 percent of Canada's carbon footprint by 2020.

"How Canada addresses [these] environmental issues," read the briefing notes, "is of fundamental importance to Canadian trade and national and international energy security."

In December of 2011, Prime Minister Stephen Harper's Conservative government set off a storm of international protest when it formally withdrew from the Kyoto Protocol.

"Bad news for the fight against climate change," is how France's foreign ministry described Canada's withdrawal.

BBC News correspondent Richard Black linked the decision to "extensive tar sands development", a sentiment shared by many international observers.

In early January of 2012, minister Oliver accused the "environmental and other radical groups" opposed to oil sands development of receiving foreign money in order to "hijack our regulatory system."

Click here to read an in-depth Tyee series about the solutions being proposed to address the oil sands industry's massive, and growing, carbon footprint.

Geoff Dembicki reports on energy and climate change issues for The Tyee.