The Prime Minister in the United Kingdom Constitution

This post was contributed by Eloise Ellis, Senior Lecturer in Law.

The famously unwritten Constitution of the United Kingdom has many quirks and unusual features, some of which have risen in prominence as a result of the current developments arising around Brexit (the abbreviation used to describe a ‘British Exit from the European Union’).

One aspect relates to the position of Prime Minister (the Head of Government) – a role which owes more to constitutional convention and pragmatism than to formal rules, regulations or statute.  Indeed, the Prime Minister is rarely mentioned in statute.  In the Westminster Model of a Parliamentary Executive all Ministers, including the Prime Minister, are drawn from one of the Houses of Parliament and for the Prime Minister this is now invariably the House of Commons.  Government Ministers, including the Prime Minister are appointed by the Queen – note it is officially Her Majesty’s Government – using prerogative powers.  Although in reality, it is the Prime Minister who decides upon the other Ministerial appointments and these Ministers are then formally or ceremonially appointed by the Monarch. 

What about the Prime Minister?  Does the Monarch have any discretion as to whom to appoint?  In practice, the answer is ‘no’.  The Monarch’s use of this prerogative power is heavily governed (or controlled) by constitutional convention.  The Monarch appoints as Prime Minister the person who is best able to ‘command a majority in the House of Commons’, this is will usually be the Leader of the largest political party in the House of Commons.  In practice, this also means that the United Kingdom can, and frequently does, experience a change of Prime Minister without the need for a General Election.  Of the past four Prime Ministers, only one, David Cameron, became Prime Minister, following an election.  The other three (Gordon Brown, Theresa May and, the current incumbent, Boris Johnson) became Prime Minister because of a change in the leadership of the party with the largest number of seats in the House of Commons. 


Do you want to find out more about the institutions of Government, including the Prime Minister and Parliament and the important role of constitutional conventions?

For students on the University of London UG Laws programmes we are running a London Study Support Event for Public Law in November. During this course, my colleague and I will be covering this topic and other important topics found in the first half of the module guide.

Full details on the VLE.

I am a Senior Lecturer at the University of East Anglia where I teach Public Law and European Union Law.  I am also a Visiting Professor at the University of Salzburg and at the Institute of Law, Jersey.  Prior to my academic career, I spent several years working as a political adviser and policy manager before spending time in a Government Department, where my roles included working for a Minister.  I am a Fellow of the Higher Education Academy and have a Master’s degree in Higher Education Practice.  I have been involved with the London International course in various ways for over ten years developing resources for Public law.

One comment

  1. Thank you Prof Ellis. Is the progation of Parliament based on a contitutional convention? How can the use of Prerogative power be used to circumvent the operation of an elected house of commons?

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