The Shadow Cabinet is made up of frontbench MPs from an official Opposition party. The Shadow Cabinet is a feature of the Westminster system of government. It comprises a senior group of opposition spokespeople who, under the leadership of the Leader of the Opposition,form an alternative cabinet to that of the government.
The Opposition party appoints an MP to ‘shadow’ each of the members of the Cabinet. In this way the Opposition can make sure that it looks at every part of the Government and can question them thoroughly. It also means that the Opposition has MPs that are ready to take specific jobs in the Cabinet if they win at the next General Election.
The term “spokesperson” is used instead of “shadow”.
The reason why only sitting MPs are chosen in Shadow Cabinet is that they should respond to policies and project government is implementing “INSIDE PARLIAMENT”.
If you are not an MP, you cannot contribute to any deliberation in the chamber. It will be USELESS to chose someone who is not an MP to be in shadow cabinet because he/she wont have a forum to speak on behalf of his/her party