The Irish parliament, or Dail, is elected by proportional representation, using the single transferable vote system.

BBC: The Dail

Labour offered to enact AV and conduct a referendum on a much more proportional system, the single transferable vote (STV).

ECONOMIST: More unites the Tories and Lib Dems than divides them

The Liberal Democrats have long campaigned for a more proportional voting system, with the single transferable vote their favoured option, but the Conservatives agreed to a referendum on AV as part of the coalition deal.

BBC: AV referendum: Union stance 'depressing', says Johnson