What must people do when the government does not do its job?

Re-elect new representatives (if it's that kind of government) or overthrow it.

When this happens the public is thrown into uncertainty and may become distrustful of any new government bodies. Of course, the right answer may not apply to the every nation as their needs are different*.

However this does not mean there isn't a core set of changes that might be necessary. A government is needed to lead a nation and without a doubt, if the predecessor fails a new regime will be assembled, even it if claims not to be a government. It will still be a body of organized people working toward a common goal, hopefully to better the quality of life for its citizens etc. If the current government of Canada falls many things could be considered to improve on the old design:

• Resist U.S./British influence at a higher rate and seek a more Canadian identity
• Allot moneys to more relevant issues
  
• Perhaps screen/monitor those wishing to become politicians

I cannot tell you what should be done as I don't know. The government should never fail and does so at a high cost to itself, meaning failure is perhaps only occasional. The fault can be placed on people wanting money enough to compromise their position as public figures so maybe we should be asking some else.

What should be done if politics became any more corrupt?

In any case, the first answer is completely correct just lacking detail.

*As cliche as it is, Middle Eastern countries and places with similar plights must be treated differently. It is this writers opinion that their existing government should be totally wiped out in favor of more open minded bodies, and many native laws taken to the trash heap. "The care of human life and happiness and not their destruction is the first and only legitimate object of good government." -Thomas Jefferson