“The current system is grossly unfair in allocating seats from votes but, more importantly, PR is the key to giving a political voice to the millions of people who reject austerity.”
Mark Serwotka, 18 May 2015

PCS union boss Mark Serwotka is calling for a change to Britain’s electoral system.

He’s not the only person to call for an end to first-past-the-post elections, which do not allocate parliamentary seats proportionally compared to the number of votes a party wins.

In a speech yesterday, Mr Serwotka suggested that a system of proportional representation (PR) would mean people who vote against the austerity plans of some of the leading parties would get more of a voice. Is that right?

The analysis

Here’s what the balance of power would look like if we used the D’Hondt method of PR, a system used to allocate parliamentary seats in dozens of other countries:

There’s obviously a big difference between this and what we actually ended up with on 8 May:

So it’s possible to have some sympathy with Mr Serwotka when he says the current system is “grossly unfair” – although this and other arguments were made in favour of switching to an alternative vote in 2011, and people rejected the change. [See update below].

It’s less clear that people who opposed austerity would have been able to exert any kind of decisive influence in a parliament elected through PR.

Let’s have a look at the first graph again. No party would have the 323 seats needed for a working majority in parliament, so some kind of coalition of power-sharing deal between two or more parties would have been inevitable.

The only two-party coalition that works numerically is a Conservative/Ukip coalition.

Both parties appeared to rule out such a deal before the election, but someone would have had to try to form a government.

It’s difficult to see how the parties perceived as being the most anti-austerity – the SNP and the Greens – could have had any power. A Labour/SNP/Green coalition would not have had enough seats for a majority under PR.

Like Ukip, the Greens would have had a lot more seats to show for the share of the popular vote they won on 7 May. But the SNP would have had a significantly smaller bloc of MPs.

And then there is a huge argument we could have about whether a vote for the SNP was really a vote against austerity.

While the party certainly claimed to offer an alternative to the public spending cuts proposed by both the Conservatives and Labour, the Institute of Fiscal Studies said: “The SNP’s stated plans do not necessarily match their anti-austerity rhetoric.”

In fact, the nationalists’ plans implied “the same reduction in borrowing over the next parliament as for Labour, although the reduction in borrowing under their plans would be slower”, the think-tank said.

The SNP denied it was misleading voters, saying the IFS had made a number of incorrect assumptions in its calculations.

During the Scottish independence referendum campaign, the SNP made the prospect of cuts to the NHS a major theme.

But both the IFS and the Nuffield Trust said Scottish governments had spent less on health than England and had failed to pass on all the money available to the NHS under the Barnett funding formula.

The verdict

For years FactCheck predicted that Ukip voters would be disappointed with how many seats the party would win despite getting a significant slice of the popular vote on 7 May.

Now calls for reform are coming from the left too. But PR would not necessarily have delivered the anti-austerity message referred to by Mark Serwotka.

In fact the most logical outcome of a 2015 election decided by PR would have been a Tory/Ukip coalition.

The SNP bloc would have been smaller. The Greens – arguably the only party who unambiguously rejected austerity – would have won many more seats but would have struggled to form part of a government.

A PCS union spokesman said: “It’s illuminating to look how much more fairly votes would have been allocated under a more proportional system, and serves to highlight just how outdated first past the post is. But that’s only half the story, what we’re also saying is that we believe FPTP skews voting patterns so changing the system would also change how people vote.”

[Update: this blog was changed on 21/05/2015 to amend the phrase “this and other arguments were made in favour of switching to a more proportional alternative vote”. We should have said that, while some supporters of AV argued it was more proportional, this was debatable. In fact, analysis suggested AV would have delivered a less proportional result in some UK elections. Thanks to readers Phil Edwards and Scott Berry for pointing this out.]