Canada is an oddball in this respect; FP. Coalition is the order of the day over most of Europe.
It doesn’t seem to be the “order of the day” in the United Kingdom, where they haven’t experienced a minority government in more than three decades. Coalition governments are extremely rare in both Canada, and the United Kingdom, because of the normalcy of majorities; when a minority suddenly appears, the constitutional waters suddenly become a little bit less calm.
If no party gets more than 50% of the seats (as is quite common in Europe), the wheeling and dealing begins to form a coalition. The side which can cobble together more than 50% of the seats forms the government (and it may not always include the biggest party).
This isn’t exactly how it works in the United Kingdom. Whether or not he can form a coalition, the first chance at government is the inherent right of the incumbent prime minister. Gordon Brown will have the first chance to govern, regardless of whatever deals are struck by the opposition parties, unless he decides to resign or the Queen’s speech is rejected by the newly-formed House of Commons.
The first act of the new government is to introduce a motion of confidence in the Parliament and get it passed. Once the Parliament expresses confidence in the government, the business of governing can begin.
This is the same in Canada; the Government introduces the throne speech, and it is debated for six sitting days before a motion for an address in reply to the speech is adopted (or rejected). The United Kingdom Government introduces the Queen’s speech, and it is debated for a predetermined period of time; routine Government business continues to take place during this period, and it can take up to two weeks for the House of Commons to come to a decision on whether or not to adopt the address in reply to the Queen.
But Canadian system is very rare (where the biggest party automatically forms the government).
That isn’t our constitutional system.
If our prime minister holds less seats than the Liberals after the next election, but no party holds an overall majority, it’s irrelevant who the largest party in the House of Commons would be; Stephen Harper would in any case have the right to meet the newly-formed House of Commons and attempt to pass a throne speech. He could have seven seats and the Liberals would have one hundred fifty, but if the prime minister could secure the House’s support, he would still have a democratic mandate to govern.