Pros:
- Simple and familiar
- Embodies a constituency link
- Favours single party government
Cons
- All-or-nothing approach - "Winner takes all"
- Number of MPs a party has in parliament rarely matches their popularity with the public nationally - disproportionate rewards for the Party with the highest level of support - with 5 parties that can lead to absolute power on the basis of a third of the vote.
- MPs are often elected with minority support. Where seats have more than 2 popular candidates - the winner can have a marked minority of support (lowest was 24.5% 2015 Belfast South).
- The most unpopular candidates can be elected
- Voters often feel they cannot vote for their first choice. FPTP encourages tactical voting
- Fosters confrontational politics, and encourages voters to vote tactically against the party they like the least, rather than for a positive political programme
- Encourages policies in manifestos which pander to swing voters and ignore core supporters
- Voters who support a party but dislike the local candidate for that party have no way of expressing those conflicting views.
- Parties focus on marginal constituencies so voters are not treated equally - voters who live in safe seats can feel and often are ignored by politicians.
- Wasted votes - surpluses in safe seats and large votes for losers in many constituencies do not translate into representation - often more than half of all votes are wasted
- Disillusionment with politics - people aware that their vote will not make a difference lose interest
