Separation of powers: legislative, executive and judiciary
Produced in partnership with Carl Gardner of Head of Legal
Separation of powers: legislative, executive and judiciary

The following Public Law guidance note Produced in partnership with Carl Gardner of Head of Legal provides comprehensive and up to date legal information covering:

  • Separation of powers: legislative, executive and judiciary
  • Source of doctrine
  • The three branches of government
  • Relevance in the UK constitution
  • Fusion of powers in the UK
  • Relationship of executive and legislature in the UK
  • The problem of executive dominance over the legislature
  • Independence of the judiciary in the UK
  • Judicial power and judicial restraint
  • Is it inevitable that powers overlap?
  • more

Source of doctrine

The origins of the doctrine are often traced to John Locke’s Second Treatise of Government (1689), in which he identified the 'executive' and 'legislative' powers as needing to be separate.

… it may be too great a temptation to human frailty, apt to grasp at power, for the same persons, who have the power of making laws, to have also in their hands the power to execute them, whereby they may exempt themselves from obedience to the laws they make…

Its classic exposition is however that of the Baron de Montesquieu, writing about the constitution of England in his L’Esprit des Lois (1748), in which he identified judicial power as the third branch of government.

When the legislative and executive powers are united in the same person, or in the same body of magistrates, there can be no liberty; because apprehensions may arise, lest the same monarch or senate should enact tyrannical laws, to execute them in a tyrannical manner.

Again, there is no liberty, if the judiciary power be not separated from the legislative and executive. Were it joined with the legislative, the life and liberty of the subject would be exposed to arbitrary control; for the judge would be then the legislator. Were it joined to the executive power, the judge might behave with violence and oppression.

There would