The English council elections will be the first major test of Jeremy Corbyn’s leadership

What Labour needs to win in local polls to give heart to Corbyn

This year people across the UK will be voting for something – for devolved assemblies in Scotland, Wales and Northern Ireland; for police and crime commissioners across England and Wales; and in London for a mayor and assembly. For Labour, though, the most keenly watched contests will be those for the town halls of England.

With the SNP looking ever more assured in Scotland, and little scope for Westminster gains in Wales, Jeremy Corbyn’s Labour party must look to England for the electoral gains it needs to challenge for government. Next month’s local elections provide the first major test of the party’s English progress under its new leader.

The basic stakes are simple: Labour in opposition needs to gain votes, win seats and take control of councils. The opposition usually does well in local elections regardless of who is in government. Labour oppositions have made an average net gain of 300 seats in local elections since 1980, and have made net losses on just two occasions – in 1982 (immediately after the foundation of the SDP) and in 1985 (when the miners’ strike and conflicts with Militant were at their height). Local government reorganisation means fewer seats are at stake now but, even allowing for that, history suggests 200-250 seat gains are a reasonable target.

Measuring vote shares in local elections is a little trickier. Councillors are elected to metropolitan boroughs, cities and districts in different years, so vote shares in one cannot be directly compared with another – some statistical adjustment is needed. Oppositions going on to win have secured projected vote shares close to 40%. The Conservatives under David Cameron averaged 39% in 2006-9, while Labour under John Smith and Tony Blair averaged 42% in the mid-1990s. Figures closer to 35% presaged defeat in 1998-2000, 2002-04 and 2011-14.

History thus suggests two targets for an opposition with aspirations to rule: a projected vote share close to 40% and 200-plus council seats gained. The last time the seats contested this year were up for election – 2012 – Labour under Ed Miliband hit these targets comfortably, gaining more than 800 council seats on a 39% projected vote share. The very strength of this performance makes it hard to repeat: most of the easiest council seat targets were already picked up last time.

Hitting a 39% vote share is also harder now, particularly with the rise of Ukip. When the seats up this May were last contested, Ukip was a side-show in local elections – it did not contest most seats, and was rarely in the running when it did. So the votes in most of the country were divided between just three parties. Since then, Ukip’s popularity has surged, and it has started putting up many more candidates. This makes Labour’s task harder as a matter of simple arithmetic – it is harder to win a dominant share now the vote in most of the country is split four ways, rather than three.

What would a strong English Labour performance look like in May? A projected share above 35% despite Ukip competition, a large lead over the Conservatives in overall vote share, and significant seat gains should be Labour’s minimum goals. It would be hard for an opposition doing worse than this to argue it is making progress in England. Early indicators suggest Labour may struggle to hit this target. Analysis of council byelections in January suggested Labour’s vote share could fall to 31%, putting 200 or more council seats at risk. Labour’s performance in council elections since January have not been much better. At present, then, losses look more likely for Labour than gains.

The outlook is even less rosy when we look outside England to the devolved elections in Wales and Scotland. Welsh Labour has been in steep decline over the past few years, while Ukip has surged, a shift Welsh expert Professor Roger Scully has called “the biggest polling movement no one has heard of”. Labour is still set to be the largest party in Wales, but its majority in the Welsh assembly is in serious jeopardy. A strong night for Labour will see it hold on to its majority; a bad night could see it fall below its previous worst performance of 26 seats.

While the Welsh party worries about defending dominance, Scottish Labour is struggling just to remain relevant. The enormous surge in SNP support since 2007 shows no sign of abating, with current polling suggesting the party will win more than 50% of the overall vote, while Labour’s share has collapsed to the low 20s, barely ahead of the Scottish Conservatives.

The party’s best-case scenario is that it keeps seat losses in single digits, and holds on in some of its 13 remaining constituencies. A bad night in Scotland will see Labour wiped out at constituency level in a country whose politics it dominated less than a decade ago.

London provides the main prospect for optimism in the current cycle. Sadiq Khan currently leads in most polling, and the London electorate – very ethnically diverse and the London electorate, with large numbers of young, cosmopolitan university graduates – should be a relatively favourable environment for the current Labour approach. A comfortable win for Khan will do much to settle Labour leadership nerves, but a failure to recover control of City Hall would be a very bitter pill to swallow.

Dr Robert Ford is a research fellow in politics at the Institute for Social Change at the University of Manchester

Good, bad or downright ugly? How results would affect Corbyn

GOOD NIGHT

■ 100-plus seat gains in English locals and 38%-plus vote share, winning control of English councils, particularly in key southern England target areas such as Worcester, Stroud and Milton Keynes.

■ A decisive win for Sadiq Khan over Zac Goldsmith in London, by a margin of 55-45 or more.

■ 31 or more seats in Wales, 30-35 seats in Scotland, a retreat from the 38 won in 2011, but a small one.

■ Results like this would enable team Corbyn to credibly claim decisive progress.

OK NIGHT

■ Fewer than 50 net seat losses in English locals on a vote share of 34-36% - worse than 2012, but in line with results since. Successful defences of key local councils in marginal areas such as Dudley, Southampton and Norwich.

■ 28-30 seats in the Welsh Assembly, leaving Labour just short of a majority.

■ Narrow 53-47 win for Sadiq Khan in London over Zac Goldsmith.

■ 25-30 seats in Scotland: a major retreat, but finishing comfortably ahead of the Conservatives.

■ Corbyn allies will point to one-off factors such as the EU referendum, the intervention of new Ukip candidates in many councils, and the dominance of the independence question in Scotland to explain away modest retreats.

BAD NIGHT

■ 200 or more council seat losses on a projected national vote share of 30-33% - a major retreat, and as bad as the worst results recorded under Ed Miliband. Labour loses control in a range of councils, including relatively favourable areas such as Derby, Rossendale, West Lancashire and Wirral.

■ Dead heat in London - 50-50 vote shares and a very narrow victory for either side.

■ 26-28 seats in the Welsh Assembly - significant losses, and close to Labour’s all-time low.

■ 20-25 seats in Scotland, a major rout, with total or almost total defeat in constituencies, and leaving Labour barely ahead of the Conservatives in Scotland.

■ The leadership would come under significant pressure as results at or near record lows will suggest significant voter hostility to their approach.

VERY BAD NIGHT

■ 400 or more council seat losses on a projected national vote share of under 30%. Loss of control in many Labour councils, and seat losses extending even to key urban strongholds such as Birmingham, Coventry and Leeds.

■ Decisive defeat in London, with Goldsmith beating Khan 55-45, outperforming Boris Johnson.

■ 25 seats or fewer in the Welsh Assembly - Labour’s worst performance in Wales.

■ Fewer than 20 seats in Scotland - Scottish Labour loses all its constituency seats and falls into third place behind Scottish Conservatives.

■ All this makes grim news indeed, pointing to a party that is in electoral freefall across all three nations of mainland Britain, and unable to score wins, even in apparently favourable territory such as London.