Could there really be a hung parliament at the next UK general election?

Rishi Sunak has boldly claimed that the Conservatives’ disastrous set of local election results prove the country is on course for a hung parliament and a Labour-led “coalition of chaos” after the general election.

The prime minister seized on research by the election experts Colin Rallings and Michael Thrasher suggesting that if Thursday’s results were replicated in a general election, Labour would fall short of enough seats to win outright.

But the problem for Sunak about this particular theory is that the read-across from local elections to a general election is quite hard to do. Here we look at some key points of difference that need to be taken into account in any such forecast.

National vote share

Many polling experts are sceptical of the usefulness of extrapolating a potential national result from local elections. “It is not an estimate of parties’ general election prospects. It is not a poll either. It is an attempt to estimate how locals result would look if everyone in Great Britain voted,” said Rob Ford, a politics professor at Manchester University.

Related: Big Tory losses but no Labour landslide. What might happen at Westminster? – a visual analysis

The places that vote one year are politically different from those that vote in another set of local elections. This year’s local council elections, for example, took place disproportionately in urban England outside London.

About half of voters who will vote at the general election did not vote in the locals, and while it is hard to know which way those votes will fall, the national polls, which put Labour 20 points ahead, are generally the best indicator of what would happen if there was a general election tomorrow.

Smaller parties

All the evidence suggests that people vote differently at local elections than they do in national polls, and are more likely to back smaller parties or independents in the former.

This time, about 23% went to parties other than Labour, the Tories and the Liberal Democrats. But while independent candidates do well in local races, they are rarely as successful in Westminster contests.

The Lib Dems also tend to get more votes at local elections, picking up 16% of the total this time, which far exceeds their performance in national polling.

Scotland

Last week’s local elections only took place in England and Wales, so Rallings and Thrasher’s analysis assumed there would be no change in results in Scotland.

At the last general election, Labour only won one seat there, a total doubled at the Rutherglen byelection in October. But the party’s fortunes in Scotland have transformed amid turmoil in the SNP, which has just elected its third leader in 14 months, and Tory chaos at Westminster.

This time round, Labour is expected to win a bigger chunk of the 59 Scottish seats available. Senior party figures think they could take more than 20 seats. While that, on its own, would not make enough of a difference, based on Rallings and Thrasher’s analysis, to win an overall majority, the Scottish seats would certainly help Labour get closer to the 326 needed to secure one.

Blackpool South byelection

The one race last Thursday where there was more obvious read-across to the national picture was the Blackpool South byelection, the only parliamentary contest on polling day.

Labour won back the seat with the third-highest swing since the second world war. It was also the fifth time in the last year when the Tories have lost a Westminster byelection with a direct swing to Labour of more than 20%.

The Tories came second, beating Reform by just 117 votes. Their vote share collapsed by more than 30 points, which split more or less equally to Labour and Reform, and prompted nerves at Tory headquarters.

If the result was repeated nationally, the Blackpool South byelection would result in there being fewer than 100 Tory MPs after the general election.

Geography

For Labour, the locals were as much about where they won votes as about how many votes were won. The key test was how they performed in battleground areas.

Its strategy of focusing resources on marginals, rather than trying to boost turnout in parts of the country where it has big majorities – such as Liverpool, London and Manchester – is likely to be repeated later this year.

Keir Starmer’s party will be bolstered by winning the East Midlands mayoralty, as it suggests a recovery in seats including Derby North, Ashfield and Bolsover, as well as by taking York and North Yorkshire in Sunak’s own backyard.

While the Tories’ Ben Houchen hung on in Tees Valley, if the 16.7% swing to Labour was repeated at the general election, it would win all five seats in the region, including Darlington, Hartlepool and Redcar.

In the final days of the campaign, Labour switched extra resources from Tees Valley to the West Midlands, which is brimming with target seats. It paid off when it beat the Tories’ Andy Street by just over 1,500 votes in a shock win.

Labour is planning to target the south of England heavily at the election, after making gains in councils including Crawley, Swindon, Thurrock, Basildon, Southend and Rushmoor, which includes the garrison town of Aldershot.

Reform UK

Reform only stood in one in six of the council wards last week, suggesting that its impact at the general election could be greater, with the party leader, Richard Tice, pledging to stand a candidate in every constituency.

In the wards where the party did stand, the Conservative vote was down by 19 points, indicating that most of its votes later this year will come from the Tories. Labour experienced a slight boost in vote share in council wards where Reform stood.

The rightwing populist party failed to beat the Tories into second place in the Blackpool South byelection – if only just – and is so far not performing as well as Ukip did in the past. But Tory fears of a return by Nigel Farage to the political frontline could change that.

‘Coalition of chaos’

Rishi Sunak is attempting to redeploy the “coalition of chaos” attack line, one of the Tories’ most successful political strategies in the past decade, which helped them secure a surprise majority at the 2015 election.

Back then, the Tories relentlessly warned that Labour could do a deal with the SNP to gain power, with attack posters showing its then leader, Ed Miliband, sitting in the top pocket of Alex Salmond, who had been SNP leader until the Scottish independence referendum.

At the time, the opinion polls were pointing to a hung parliament. The strategy was seen to have convinced some voters, particularly those in the so-called blue wall who had previously backed the Liberal Democrats, to vote Tory.

However, the best part of a decade of political chaos on the Conservatives’ watch since then raises questions about the potential success of revisiting the strategy. From Brexit to Partygate to Liz Truss’s disastrous mini-budget, it seems unlikely that voters will be convinced by Sunak’s attempts.