Rev. 15 Dec 25
Where. AMS is used in Scottish parliamentary elections and in elections for Greater London Assembly. It is also currently used in elections for the Senedd (Welsh Parliament), but that will change to pure D’Hondt in 2026.
What. The Electoral Commission website says:
Constituency candidates are elected using the first-past-the-post. Once the constituency votes are counted the candidate with the most votes is declared elected.
The regional votes are then counted. The Regional Returning Officer add up the total regional votes from all of the constituencies in their region cast for parties or individual candidates. They will also add up the total number of constituency seats won within the region by each registered party.
The number of votes cast in the regional ballot for each registered party or individual candidate is divided by the number of constituency seats gained, plus one. After that calculation is done, the party with the highest figure gets the first regional seat. To allocate the second to seventh additional seats the calculation is redone, but each time any additional seats gained are added into the calculation.[1]
Why. If we want party proportionality above all else, then pure D’Hondt is the simplest and most widely used option. If we aspire to have party proportionality but at the same time wish to retain a link between MPs and constituents, then AMS is offered as a reasonable, tried, and widely supported, compromise solution.
But there are problems.
Why not. There is much support for the adoption of AMS, but also some objections.
► A few are opposed to the introduction of multi-seat election, favouring the direct connection between an MP and their constituents. But AMS partially addresses this by having a single-seat constituency component in addition to its regional component.
► Some will object on the grounds that under AMS it is parties rather than the voters who decide who their MPs will be. Which AMS does as a simple way of ensuring “proportionality”. In any case, it is not so different to what happens now, particularly in safe seats. And AMS partially addresses this problem by having its single-seat constituency component.
► FPTP in double-sized constituencies[2] could make it unreasonably difficult (twice as hard) for an independent or a small party to gain a seat.
First past the post. AMS would continue to use FPTP in the election of its constituency MPs. The faults in FPTP may be deemed to matter less when used within AMS because the overall system is more or less party proportional, in a roundabout way. On the other hand, they may be deemed to matter more because they are more likely show up in AMS’s double sized constituencies and will be in no way corrected in the regional ballot in which it is the parties rather than the voters who choose the MPs.
The bottom line is that FPTP is wrong in principle and PV is right in principle. It is close to incredible that, aware of the dreadful faults of FPTP, we would choose to switch to a system which uses FPTP for half the seats. AMS would be a very much better system if constituency candidates were elected using PV rather than FPTP.
The regional vote. There is also scope for PV in the party-list component of AMS.
Where there are more parties standing than there are seats available, as used to happen in the UK’s elections for the EU Parliament, it seems unacceptably undemocratic to disenfranchise supporters of parties who could not possibly win. Much fairer to eliminate those parties and to transfer the votes they had received to the second choices of those who voted for them. PV is the obvious way of doing that[3].
Moreover, when D’Hondt grants a party a second seat, the number of available seats decreases but the number of active parties does not. So at that point we should similarly eliminate the party who could not possibly win a further seat.
Furthemore, some countries’ D’Hondt-based systems disallow parties with less than a given threshold level of support (typically from 2% to 5%). If we were to enact such an exclusion[4] then the same PV-based elimination mechanism should apply.[5]
When. Perhaps more significantly, a serious short-term problem is that AMS is extremely unlikely to be feasible before the next UK election. It will take considerable time to formulate and enact the necessary legislation. To prepare for AMS then requires boundary changes, if only grouping of constituencies into pairs and into new regions. And then further time is needed to allow political parties and local administrators to reorganise to the new structure. Early implementation seems distinctly infeasible.
So if we pursue AMS to the exclusion of any more immediate solution then it should be assumed that we shall have to endure at least one more general election under FPTP. Not a cheerful prospect.
A conclusion. Raw AMS is significantly undemocratic. AMS with PV is clearly much better.
So if it is AMS we want then the best plan would be
a. to introduce PV now, in time for the next election
b. to extend this as soon as possible thereafter to an improved version of full AMS
. – with PV rather than FPTP for the election of constituency candidates
. – preferably with PV to shorten the list of parties to the number of seats available.
[1] In other words, it is D’Hondt (q.v).
Note that the ability of FPTP to elect a candidate on a minority of votes greatly increases the chance that a party will win more constituency seats than the regional D’Hondt would have allocated in total.
[2] We assume that seats are 50:50 constituency/regional. So if UK is to have the same number of MPs then the constituencies have to be twice as big as with pure FPTP.
[3] Each party eliminated would of course be the one with the lowest current voting weight,
i.e. (Current votes for)÷(1+Number of seats won so far).
[4] Which cannot be recommended, even if it has the support of all the larger parties.
[5] Wiki says: “The modified d’Hondt electoral system is a variant of the d’Hondt method with an electoral threshold for parties. Votes for parties below the electoral threshold are transferred to other candidates according to the single transferable voting method. This electoral system was used in 1989 and 1992 Australian Capital Territory elections.” [NB The “single transferable voting” can only mean “single-seat preferential voting”.}