The findings again weakened sterling which had earlier fallen nearly a cent against the US dollar on the YouGov model before rising on a Kantar poll which showed May's lead had increased to 10 percentage points.
A later poll, a separate regular survey carried out by YouGov for Thursday's Times newspaper, showed May's Conservative Party just three percentage points ahead of the Labour opposition, which has been eating into her lead since the start of the campaign.
This would be a shocking result - especially as Theresa May broke the vow she made at least six times not to hold a snap election as it would not be in the nation's best interest as she said that an even bigger mandate in parliament would give her a bigger mandate in Brexit negotiations.
"The Conservatives have maintained the lead in polls, including yesterday's ICM poll, and are the favourites to win".
"Recently we've been relatively agnostic about sterling, but have now chose to underweight the currency for the next couple of weeks, in case the depreciation accelerates", Cosimo Marasciulo, head of European fixed-income at Pioneer Investments, said in emailed comments.
But if she fails to beat the 12-seat majority her predecessor David Cameron won in 2015, her electoral gamble will have failed and her authority will be seriously undermined.
That would have uncertain consequences for Britain's $2.5 trillion economy, and future government policy on everything from government spending and corporate taxation to bond issuance.
Later, research company Panelbase put Theresa May's lead over the Labour Party at 15 points.
During the European Union referendum campaign it consistently showed that more voters favoured Leave than Remain.
"The sharp recent reduction in the party's lead, poor poll reliability in past votes, plus an unusually high level of uncertainty about the key issues and how different groups could vote, make this election tricky to call", he said. Instead, May sent her interior minister, Amber Rudd, who dismissed the leaders as members of a "coalition of chaos".