LONDON (Reuters) - Just over five weeks before a referendum on whether Britain should stay in the European Union, the message from opinion polls is simple: It is impossible to predict how Britons will vote on June 23.
Opinion pollsters that failed to forecast both Prime Minister David Cameron’s unexpectedly decisive election victory and the result of Israel’s election last year have so far painted contradictory pictures of British public opinion.
Traders woke up on Tuesday to an ORB telephone poll showing a 15 percentage point lead for the “In” campaign, a reading that sent sterling up to a 2-1/2 year high against the euro.
But within hours a second poll, conducted online by TNS, showed the “Out” campaign with a three-point lead.
“What is the bottom line? I don’t know. I don’t know what you should take away from it. There is clearly a difference between the telephone and the online polls,” Johnny Heald, managing director of ORB, said in a telephone interview.
“The evidence is that a lot of people are not excited about saying they want to remain: the passionate people here are those who want to leave. I think the status quo is less sexy but also less risky,” said Heald.
In a research note for clients entitled “Brexit: latest batch of polls adds to the uncertainty”, JPMorgan said: “One should not be confident about the message coming from the polls, however one reads them.”
A British exit would rock the European Union -- already shaken by differences over migration and the future of the euro zone -- by ripping away its second-largest economy, one of its top two military powers and by far its richest financial center.
From U.S. President Barack Obama to the International Monetary Fund, a host of world leaders and international organizations have cautioned British voters about the risks of leaving the bloc it joined in 1973. The Bank of England said last week that Brexit could tip the economy into recession.
Israel’s leading pollsters were left red-faced after failing to predict that Benjamin Netanyahu’s Likud party would comfortably win a general election in March 2015, maintaining until voting day that the centre-left would come out on top. Even exit polls on the night proved unreliable.
Cameron’s clear victory in the May 2015 election prompted British pollsters to hold a post mortem into their failure to predict the result. The answer? Sampling methods.
Pollster ICM pollster released telephone and online polls on Monday whose results contradicted each other completely. The phone poll put “In” ahead on 47 percent, while the online sample showed “Out” in the lead on 47 percent.
“Bemused? You have every right to be,” said Martin Boon, director of ICM, in a commentary accompanying the polls. “If you want to ask me, which is unlikely, the answer you’d get is ‘I just don’t know’.”
Such is the confusion over the polls, which now often move the pound, that some investors prefer to look at betting markets which have proved a better predictor of some political events, including last year’s British and Israeli elections.
Odds there have consistently shown British voters opting to remain in the 28-nation EU.
Online brokerage IG Group said its referendum barometer was showing a record high for “In” on Tuesday, with a 74.5 percent chance, while Betfair’s odds gave an implied 73 percent chance of a vote to remain.
Campaigners on both sides say privately that they do not have a clear picture of what is going on with voter opinion from the public polls. They are using private polling and both sides draw comfort from surveys showing their favored result.
Lynton Crosby, the strategist who helped Cameron win last year’s election, wrote in a commentary on the ORB poll: “Time may be running out for the ”Leave“ camp to make the case for Brexit.”
But he added that Cameron’s campaign had one big challenge: to get pro-Europeans to vote on polling day.
“If the Britain Stronger in Europe does not have a sufficiently strong grassroots network to get people to the polls, many voters could wake up to a surprise on June 24.”
Additional reporting by Ana Nicolaci da Costa; Editing by Catherine Evans and Gareth Jones