These are derived from the fact that the members of the cabinet are Members of Parliament, and therefore accountable to the House of which they are a member. The Queen will only appoint a prime minister whose government can command the support of the House of Commons, which alone can grant supply to a government by authorising taxes; and the House of Commons expects all ministers to be personally accountable to Parliament. In practice, Cabinet ministers will usually have a junior minister to represent their department in the House of Lords.