The second principle of fusion of legislative and executive powers is key to the working of the parliamentary system. Govenments are not directly elected by the people, individual members of parliament are, and from these members of parliament, the government is chosen, that is the Prime Minister and his Cabinet ministers. This is done through the process of an election of competing political parties. Shpuld any party emerge with the majority of seats, the leader of that party is called upon by the Governor General to form a government. He does this by appointing members to his Cabinet and together they govern at the will/consent of parliament. If parliament withdraws its support, non-confidence is declared and the government must resign. This is not a law but a convention, based upon custom and usage and strictly respected.
The Prime Minister and the Cabinet also function on the basis of convention (the office of Prime Minister was never created by law but developed over the centuries of British practices. The Cabinet is also based on those practices and operate as the active part of the Privy Council, and is beholden to the PM who appoint and can thus dismiss them. They serve "at his pleasure".
The Prime Minister and the Cabinet are bound by the principles of collective and ministerial responsibility. This means that they are responsible, and held accountable for their actions. Collectively the Cabinet and individually each minister has to answer to parliament and if they are found wanting, parliament can take various actions against them. They can be reprimanded or they can be forced to apologise or they can be suspended or they can be expelled and even imprisoned. Ministers usually accept responsibility and thus spare the government any embarassment and a possible vote of non-confidence, though this is almost impossible when the Government is a majority. In this case the Opposition can raise questions and use the public forum to harass and expose them in parliament and the media or through a Commission of Enquiry , as was the case of the last Liberal government, who suffered an ignominious defeat in the last election over the revealations of the Gomery Commission.
Government accountability is crucial to the survival and success of the parliamentary system. Without it, govenment can run rampant, become arbitrary and lose legitimacy. They cannot lie to or mislead parliament. They must be answerable to parliament and respect the rules and accept the responsibility when things go wrong.
The Harper government and the Defence Minister Peter MacKay are being accusedof lying to and misleading parliament over the cost of the F-35 fighter jets. So far they have been desperately fighting against these accusations, but as more and more details are revealed, the pressure will build for someone to take responsibility. If it were anyone else other than Mackay, he would have been(like Guerges) served up as scarifice. Mackay is a different "can of beans". He was the one who led the Conservative Party (as leader) into a union with the Reform Party and so has clout (previous questionable actions, like using military helicopter to go fishing, has seen Harper defending him).The heat that the Opposition can generate and the extent of public outcry will determine his fate. One thing is certain and that is Harper will not take responsibility even though as Prime Minister it is his responsibility. Collective responsibility or individual responsibility? Both but Mackay can do the "honorable" thing and "fall on his sword". Don't bet on either but on the Government toughing it out to the detriment of "parliamentary democracy"