Westminster vote system 'is broken'
The report from the left-of-centre Institute for Public Policy Research comes ahead of the 5 May referendum on replacing first-past-the-post (FPTP) with the alternative vote (AV) system, under which voters rank candidates in order of preference.
While supporters of FPTP - including most Conservative and Labour MPs - argue it is the best way of producing strong governments, the new report argues that long-term changes in voting patterns mean the system has become a recipe for hung parliaments and coalitions in future.
IPPR director Nick Pearce said: "Unless first-past-the-post is reformed, the UK will be left with a voting system that neither delivers fair representation nor single-party government."