On the eve of a parliamentary report on the financial cost of the Afghanistan mission for Canada, an independent group has released their own answer on the subject: $28 billion.

The Rideau Institute, an advocacy group and think tank that largely opposes Canada's military participation in Afghanistan, said the mission will cost the government $20.7 billion by 2011.

In addition, the Institute said the direct and indirect costs to the Canadian economy due to soldiers' deaths and injuries will be about $7.6 billion.

Parliamentary budget officer Kevin Page will release his report Thursday morning at 11 a.m. ET. The report was due to be released last month, but concerns of interfering with the election led Page to delay the release -- although Canadians will head to the polls on Tuesday.

The Conservatives have pegged the cost of the Afghanistan mission from 2002 to 2008 at about $8 billion. A significantly higher cost could be a political problem for Harper.

Support for the mission is lowest in Quebec, where the Tories are struggling to gain seats in the election.

Steven Staples, president of the Rideau Institute and co-author of the report, said he may be taking it a step further than Page's estimate, but obviously won't know until Thursday.

"We took it a second step further by also looking at the loss to the economy of the wounded and killed soldiers," he told CTV.ca.

He said he based his estimate on some American studies that looked at the financial cost of the Iraq war, and included the price to health care. One such study was authored by Nobel prize-winning economist Joseph Stiglitz. In 2006, he suggested the Iraq war had cost the U.S. $2 trillion, about 10 times the amount previously thought.

Staples said the war in Afghanistan has also come at the cost of Canada's contribution to UN peacekeeping missions.

"We've given up so much in this war, not just in terms of government costs but also the lost contributions of all these young men and women that have died, and also internationally -- we're contributing a lot less to UN peacekeeping where we used to do a lot more," Staples said.

"We used to be Number One in the early 1990s. We had more than 1,000 troops involved in UN peacekeeping. Now we're down to something like 160. In fact, we send more police for UN peacekeeping than soldiers, so when you count the number of soldiers involved it's roughly 50 or 60."

Another report on the cost of the Afghan mission by David Perry, a former deputy director of Dalhousie University's Centre for Foreign Policy Studies pegged the bill at $22 billion.

In light of the global economic downturn and a diminishing budget surplus, Staples suggested the Afghanistan mission could put significant stress on government coffers.

"It's clear that the government's budgetary and foreign policy hands will be tied if it intends to keep our troops in Afghanistan through December 2011," Staples said earlier Wednesday in a news release.

There are about 2,000 Canadian soldiers based in Afghanistan's volatile Kandahar province.

Since the mission began in 2002, 97 Canadian solders and one diplomat have been killed in Afghanistan.