Prime Minister Stephen Harper and his strategists see this week's G-8 summit as an occasion to polish off his credentials on a larger stage, a chance to demonstrate that he has refined his international act after more than a full year in office.

But whether they like it or not, it is the increasingly unbridgeable gap between the prime minister's positions and the realities of his political situation that this week's European tour is also showcasing.

So great has the distance between the two become over the past 17 months that it begs the question of whether Harper speaks for himself or for Canada when he addresses other world leaders.

On some of the defining international issues of the day, that fact is that the prime minister is unable to put Parliament's money where his minority government's mouth is.

That disconnect was immediately apparent on Monday, the first full day of Harper's ongoing tour.

In front of a blue-ribbon audience in Berlin, the prime minister savaged Canada's environmental record under its previous Liberal government, showcasing himself as a bridge-builder between divergent approaches to global warming.

Meanwhile on Parliament Hill, the three opposition parties used up the bulk of question period to carpet-bomb Harper's positions, describing him as a saboteur of the international front to deal with climate change.

The relatively rare sight of a prime minister and its opposition at each other's throats across the expanse of an ocean is the culmination of a year that has seen the Conservative government isolate itself in the Commons and in public opinion on the top global issues on its plate.

At this time last year, Harper could boast that he had just secured parliamentary backing for extending the Afghan mission to 2009.

But now, a year later, he would hit a solid wall of opposition if he wanted to extend the deployment beyond that deadline.

That in turn makes it awkward for the prime minister to preach continued engagement in Afghanistan to his allies this week.

At this time last spring, the government was just setting out to put together its own plan to deal with the climate warming and the jury was still out on its environmental intentions.

A year, two environment ministers and two versions of a green plan later, Harper has to circumvent the Commons to implement his policies.

Even as he is telling other world leaders this week that there is a life as a champion of the environment outside of the Kyoto Protocol, his government is playing hide-and-seek in both houses of Parliament to avoid having the will of the opposition parties to have Canada fulfil its obligations under the treaty imposed upon it.

In the past, Canada has had prime ministers who have found solace, if not salvation, on the international scene at a time when their fortunes were much less promising than Harper's.

Pierre Trudeau, Brian Mulroney and Jean Chretien played undiminished roles as international power brokers even as they endured less than glowing reviews at home.

Chretien was already considered a lame duck leader when he dealt with the highly divisive issue of Iraq.

But this is different.

Harper is selling abroad a product he cannot get approved by Parliament and, so far, dare not test on his domestic election market.

Until he does, his capacity to play a leadership role on the international scene will, for obvious reasons, be more severely limited than that of his predecessors.