A referendum may be held in response to pressure over a particular issue.
The EU referendum in 2016 was promised by David Cameron if the Conservatives were re-elected in 2015. Cameron made this promise because of political pressure, and the fear of losing votes to UKIP in the general election.
A referendum can be called to ensure significant government initiatives have public approval.
The 1997 devolution referendums in Scotland and Wales legitimised devolving some powers to both countries.
A referendum can result from a deal made between political parties.
The 2011 AV electoral system referendum was agreed as part of the Conservative and Liberal Democrat coalition government agreement in 2010.
Devolution/Independence: In 2014 Scotland voted against becoming an independent country, and in 2016 the UK voted in favour of leaving the EU by 51.9% to 48.1%.
Election system: In 2011 the UK voted against changing from FPTP to AV for general elections by 67.9% to 32.1%.
A number of referendums have taken place in the UK on devolution:
In 1997 referendum votes supported devolving power to Scotland and Wales.
In 1998 there were referendum votes in favour of devolving power to Northern Ireland and establishing a London Mayor and Assembly.
In 2004 regions in England voted on regional assemblies. The North East of England rejected an assembly, voting 78% against the proposal.
Referendums increase the political awareness and education of voters over key issues.
Some UK referendums have high turnouts, such as 81% in the 1998 Northern Ireland GoodFriday Agreement referendum and 84.6% in the 2014Scottish independence referendum.
Referendums which have a clear outcome resolve political arguments.
In 1997 Scottish Parliament referendum over 74% of people voted in favour of a Scottish Parliament which addressed the issue of whether Scotland should have its own parliament.
Referendums give citizens the chance to make decisions directly, which is important in a democracy. A referendum gives the electorate a chance to voice their view on a single issue.
Referendums hold the government to account in between elections which only gives voters the power to influence decisions every five years.
Referendums challenge parliamentary sovereignty as decisions are made directly by the public rather than MPs.
Elected politicians should be making decisions on complex political issues rather than the general public who do not have the expertise.
The EU referendum was on a complex issue that some people believe the public was not informed enough to make a rational decision on when voting.
The way in which questions are phrased and the timing of them can manipulate results.
The wording of the 2016 EU Referendum was changed from "yes/no" to "remain/leave". This is because "yes/no" questions may benefit the "yes" side.
The electorate can be influenced, particularly by political figures, campaigns or the media.
People may vote with their emotions rather than considering all of the options available.
There is often low participation and voter turnout in UK referendums which limits how legitimate the referendum decision is.
Governments make the decision to call a referendum and hold them for their own political purposes.