LONDON (Bloomberg, Reuters) - Support for Britain to leave the European Union is pulling ahead of that for remaining in the 28-member bloc, reports and a polling firm said on Monday (June 6).

A YouGov poll for ITV for ITV's "Good Morning Britain" programme put"Leave" voters at 45 per cent and "Remain" at 41 per cent. The poll was based on a survey of 3,405 people last Wednesday-Friday.

In another survey of 1,213 Britons by polling firm TNS conducted in the third week of May showed 43 per cent of respondents wanted Britain out of the EU, while 41 per cent wanted it to stay, the company said.

Sixteen per cent of respondents were undecided.

Britons vote on June 23 on whether to remain in the EU, with important implications for its trade, economic and political status.

The question for politicians and pollsters studying the current referendum is whether recent polls showing Leave in the lead, including the YouGov survey, are just a symptom of another wobbly weekend before a clear victory for PM David Cameron or a sign that his luck has run out.

Two years ago, days before Scotland voted whether or not to stay in the UK, a YouGov poll suddenly showed the Leave side ahead.

The pound plunged, the prime minister panicked - then Scotland voted to stay in the UK by a 10-point margin.

Pollsters aren't much help. Having been burned in last year's UK general election, when they failed to predict that Cameron's Conservatives would win a majority, many have doubts about the reliability of their work on the referendum.

The pound fell last week when ICM published online and telephone polls both showing Leave ahead. Martin Boon, a director at the company, said he was highly unsure of the outcome.

"It's hard to think of a more bewildering electoral event," he said. "The polls have not really moved, and more phone polls of late with their pro-Remain tendencies have added to or created the narrative that Remain might cruise it. But that could be a false narrative, and for me the only correct thing to continue to say is: I just don't know how this will go."

Polling Skepticism

A year-long inquiry into the May 2015 UK election polling failure concluded that the main problem was unrepresentative samples, and that this would be hard to fix. Instead, the inquiry urged the public to be more skeptical about polling.

If more reason were needed to doubt the EU referendum polls, they don't even agree on a picture. Online polls have tended to show the two sides tied, while telephone ones have put Remain ahead.

It's not just pollsters who are anxious. People within the Leave campaign, speaking on condition of anonymity, said they thought those who expected a clear win for their side were being far too complacent. In particular, they had doubts about whether their supporters could be relied on to turn out and vote - posing another problem for polling.

"There's a discrepancy in levels of motivation," said Joe Twyman, head of political polling at YouGov.

"There are millions of people who would walk barefoot across broken glass to vote to leave. The Remain campaign doesn't have people who feel the same way. I still think we'll vote to stay, but that's assuming that there's a move towards the status quo in the final days."

The Remain campaign's problem is that it needs young people to vote - and they are the ones least likely to do so, according to Twyman. He said they needed endorsements from young celebrities, such as the junior members of the royal family.

"If I were the Remain campaign, what I'd want is for William and Harry to come out in support, perhaps in an accidentally-on- purpose open mic moment."

Voter Attitudes

Those running the Remain campaign aren't simply looking at the headline numbers. They're more interested in polling that shows voter attitudes, and here, too, there's cause for concern. Remain's core message is that a Brexit will make the country poorer. Yet 58 percent of respondents to an Ipsos Mori poll published last week said they didn't think leaving the EU would affect their own standard of living - indicating the government's message has yet to get through.

But some pollsters are less uncertain. Tom Mludzinski, director of political polling at ComRes Ltd, is more confident of a Remain win.

"Leave have the hard work to do to convince and persuade voters," while Remain "have to motivate voters," he said, noting that polls have traditionally understated the status quo option of staying in the EU, and phone polls are largely showing comfortable leads for Remain. "For a high chance of Brexit you'd want to see a consistent lead for Leave, which they haven't yet had." Tywman put the probability of a Brexit at about 33 percent. Betting markets are fast catching up with that, according to Oddschecker, with the implied probability of a Brexit rising to 30.2 percent at 5.02 p.m. on Sunday, up from a low of 19.7 percent on May 26. Matt Singh, polling analyst at NumberCruncherPolitics, had the probability at 21.7 percent.

Evidence 'Patchy'

"There are some signs of swing towards Leave, but the evidence is patchy and not entirely consistent," Singh said. "Even though Leave may have caught up a bit, it's still behind and time is running out."

Damian Lyons Lowe, chief executive of Survation, was skeptical about polls showing Leave ahead. He suggested people who took part in online polls might be more engaged with the news, and therefore affected by the media narratives, than the ordinary public.

"The movement in the polls might be right, but the lead we should be wary of," he said of the Leave campaign.

"Over the next couple of weeks, worry about Brexit will increase, volatility will increase, but the probability of things happening that will help them will drop."