The 2010 UK election is a good illustration of the problem. The Tories got 47% of the seats with 36% of the vote, but the difference between Labour and the Libdems really illustrates the problem. Labour recieved 29% of the votes and that gave them 40% of the seats in parliament, the Libdems did slightly worse than Labour with only 23% of the vote but that only gave them 9% of the seats.
I think the 2015 election with the SNP, Lib Dems and UKIP is another good example of how rubbish FPTP is:
Party | Votes | Seats | % of votes | % of seats |
---|---|---|---|---|
Lib Dems | 2,415,916 | 8 | 7.9 | 1.2 |
SNP | 1,454,436 | 56 | 4.7 | 8.6 |
UKIP | 3,881,099 | 1 | 12.6 | 0.2 |
How anyone can look at a table like the above and think "Yes, FPTP is working perfectly and there are no problems with our electoral system" is beyond me. I dislike UKIP an awful lot but the idea that a party can win over 12% of the popular vote and end up with just 0.2% of the seats is perverse. Meanwhile another party can win 4.7% of the popular vote and due to a strong regional basis ends up with 8.6% of the seats is equally perverse. FPTP is just utterly unfit for purpose and it would be hard to persuade me otherwise.
Have to say personally I quite like the look of the AMS that is used up in Scotland. Presumably (and obviously roughly!*) in such a universe the above election result would have seen UKIP gain it's solitary constituency MP but it would have gained several more list MPs whilst the SNP would have still got all their (or a similar number of) constituency MPs but likely only gained a bare handful of list MPs (if any) whilst the other parties would have had more list MPs whose regional assignation was Scotland. Sounds much fairer to me!
* Because such a thought experiment doesn't account for changes in voter behaviour under a different electoral system nor indeed what changes to the number of constituencies and MPs in Parliament might be in such a system!