Some of the polls before the general election may be overstating Labour’s huge lead over the Conservatives, a Tory election expert has said. According to Robert Hayward, a peer and former MP who first identified the phenomenon of “shy Tories” before the 1992 election, his analysis of local election results suggests that the Conservatives are getting more support from voters who say they are undecided than is showing up in the polls. “About 33 years on, I am yet again convinced that a statistical bias exists in the polls,” he said. Polling in the run-up to the election has shown commanding leads for Labour of more than 20 points in some surveys, such as YouGov, while others, such as Opinium, show a gap of about 14. Some constituency-level polling by YouGov suggests the Conservatives are heading for near wipeout. Its April projection points to more than 400 seats out of 650 going to Labour. Most experts, MPs and political strategists across the parties agree that Labour is almost certainly heading for victory, but the size of its lead will determine its majority in parliament. Hayward said it was “not shy Tories” all over again, and that Labour still undoubtedly had a large lead over the Conservatives, but he was concerned the polls were “getting it wrong”. “I think the biggest problem for me is how you allocate the Conservative 2019 voters who are now ‘don’t knows’. I do believe the ‘don’t knows’ will vote in fairly large numbers, and the indications from local council results is that they are beginning to break towards the Conservatives. “Because of the lack of commitment displayed so far, I’m not sure where things are going to end up, because events during this election could have more of an effect than in many elections because there are so many undecided.” One polling industry expert also agreed there was a risk the polls could contain methodological or structural errors. They said: “I think there are lots of reasons to be concerned about a polling error this time around. There are serious data quality issues across the industry, where it’s getting tougher to ensure the people taking part in surveys are real, taking the surveys seriously, and representative of the wider population. Pollsters are working harder to combat it, but that task is getting tougher, and there is a risk that it affects the accuracy of the polls this election. “The other issue is undecided voters. There’s three times more people who voted Conservative and are undecided than voted Labour and are undecided, and where these voters end up going will make a big difference. The pollsters make different assumptions about this group … The range of this is probably like Labour 1997 to Canada 1993 – it’s a Conservative party historic defeat with one methodology, to complete wipeout with another methodology.” They added: “The last thing is that polls do tend to be less accurate in elections with lots of change. Polls were fairly inaccurate in 1997 but it didn’t matter, because the result was so decisive. When there are more voters moving between parties, polls become more chaotic, their accuracy tends to decrease.” Anthony Wells, head of European political and social research at YouGov, said it was likely that the differences between each company’s surveys would narrow as polling day approached. “There are still a substantial number of people who voted Tory in 2019 saying ‘Don’t know’ when asked how they will vote,” he said. “A large amount of the difference in leads between different polling companies is because of different choices in how to handle that. Some companies choose to model or predict how those people will vote come election day, while others report only what people currently say. “It is as much a philosophical decision as anything else. Are we measuring how people say they will vote, or predicting how we think they will vote? Either way, it is reasonable expectation that the differences between pollsters will narrow in the lead-up to July 4 as the number of people saying ‘Don’t know’ falls. However, whether that results in a narrowing lead or not depends on to what extent, if at all, those voters return to the Tory party.”