It's a convention rather than a rule. Parties in the Opposition started creating a Shadow Cabinet so they could show that they would be prepared to run the government if they were in power. It also meant that the Leader of the Opposition could be kept up to date on issues like education, health and finance.
The Shadow Cabinet was created in 2006-09.
Shadow Cabinet of Michael Foot ended in 1983.
Shadow Cabinet of Michael Foot happened in 1980.
Shadow Cabinet of Michael Foot was created in 1980.
Shadow Cabinet of James Callaghan ended in 1980.
Shadow Cabinet of James Callaghan happened in 1980.
Shadow Cabinet of John Smith was created in 1992.
Shadow Cabinet of John Smith ended in 1994.
Shadow Cabinet of John Smith happened in 1992.
Shadow Cabinet of James Callaghan was created in 1979.
The Practice of Shadow cabinet was originate in Great BritainThe Shadow Cabinet (also called the Shadow Front Bench) is a senior group of opposition spokespeople in the Westminster system of government who together under the leadership of the Leader of the Opposition form an alternative cabinet to the government's, whose members shadow or mark each individual member of the government. Members of a shadow cabinet are often but not always appointed to a Cabinet post if and when their party gets into government. It is the Shadow Cabinet's responsibility to pass criticism on the current government and its respective legislation, as well as offering alternative policiesGULFAN ALI HASHMI FROM HIMACHAL PRADESHMOB. 9418319810
The Shadow Cabinet is led by the Leader of the Opposition, who also appoints a Shadow Chancellor and a Shadow Secretary for each Department of the Government. There's about 20 positions in total.