OTTAWA — Justin Trudeau will rapidly and radically transform the way Canadians elect their federal government if his Liberal Party forms government after this fall's election.

Trudeau, at a splashy campaign-style event here Tuesday, said that within 18 months of becoming prime minister, his government would table new rules that would make it mandatory for all Canadians to vote and change the way the House of Commons is composed that would almost certainly see more MPs from smaller and regional parties such as the Green Party and the Bloc Quebecois.

The electoral reforms Trudeau proposed Tuesday would be complemented by some other changes to the way Ottawa works. The political files of the prime minister and cabinet ministers would become subject to access-to-information laws -- they are currently exempt -- and there would be new rules that spell out the limits of how much political work registered charities can engage in.

But the most radical reform of all would be to ditch the first-past-the-post system used since Confederation to elect members of Parliament. Under this system, a candidate becomes a member of Parliament simply by getting more votes than any other candidate in a local riding even if that candidate fails to win a majority of votes cast.

The big criticism for first-past-the-post systems is that parties can form majority governments -- and, thus wield great power -- even though it wins only a minority of votes cast across the country. Both the current Harper majority and the last Jean Chretian majority government in 2000 got their mandates with only about 40% of all votes cast. Harper's majority, as well, has many regional distortions, with only a handful of MPs from Quebec and from Atlantic Canada.

Trudeau proposes to mixed system in which some MPs would win spots in the House of Commons according to their proportional popular vote of the party.

Example: The Green Party wins 3.9% of the popular vote in an election but just one seat in the House of Commons.

The Liberal propose, under the new system, the Greens would be allocated about 4% of the all the seats in the House of Commons (12 seats). That also give the party "official party status" under House of Commons rules entitling Elizabeth May and other Green MPs to seats on powerful House of Commons committees, tax dollars for research budgets, and more slots in daily question period.