<P> In theory the prime minister or premier is first among equals . However, the prime minister is the person from whom the head of state will ultimately take advice on the exercise of executive power, which may include the powers to declare war, use nuclear weapons, expel ministers from the cabinet, and to determine their portfolios in a cabinet reshuffle . This position in relation to the executive power means that, in practice, the prime minister has a high degree of control over the cabinet: any spreading of responsibility for the overall direction of the government has usually been done as a matter of preference by the prime minister--either because they are unpopular with their backbenchers, or because they believe that the cabinet should collectively decide things . </P> <P> The shadow cabinet consists of the leading members, or frontbenchers, of an opposition party, who generally hold critic portfolios "shadowing" cabinet ministers, questioning their decisions and proposing policy alternatives . In some countries, the shadow ministers are referred to as spokespersons . </P> <P> The Westminster cabinet system is the foundation of cabinets as they are known at the federal and provincial (or state) jurisdictions of Australia, Bangladesh, Canada, Pakistan, India, South Africa, New Zealand, and other Commonwealth of Nations countries whose parliamentary model is closely based on that of the United Kingdom . </P> <P> Under the doctrine of separation of powers, a cabinet under a presidential system of government is part of the executive branch . In addition to administering their respective segments of the executive branch, cabinet members are responsible for advising the head of government on areas within their purview . </P>

What are the main roles of the cabinet