Sterling fell on Friday on concerns May's lead was under pressure but climbed to the day's high against the dollar on Tuesday after the ICM poll.
Britain's pollsters are more dramatically divided about the outcome of this election than ever before, with the latest poll from Panelbase putting the Conservatives 15 points ahead of Labour, while YouGov on Thursday put the Tory lead at just three points.
The Financial Times came out publicly for May, saying she was the safer bet, though The Sun newspaper, Britain's top selling paper, cautioned that May's campaign was far too defensive.
That is because markets initially pencilled in an increased Conservative majority - strengthening the Prime Minister's hand politically as she prepares for Brexit negotiations.More news: Nest security camera knows who's home with Google face tech
"Where do you think Theresa May is tonight? Don't give her yours". "And even if his promises are practically impossible and economically catastrophic, set against the Tories' unnecessarily defensive campaign it's small wonder he appears to be picking up support". Farron said later. "The prime minister is not here tonight".
The debate itself was a boisterous affair, covering Brexit, the economy, public services, climate change, immigration and security - a major issue after the Manchester attack last week.
Sensing the momentum, Corbyn made a last-minute decision to attend a live television debate Wednesday with other party leaders - and challenged May to join him.
But many commentators believed she also saw the opportunity to wipe out Labour, apparently floundering under weak leader Corbyn.
This has been largely due to concerns about Britain's latest polling data and rising uncertainty about the upcoming United Kingdom general election.More news: Four-goal Kane shines as Tottenham hammer Leicester in PL clash
They showed Theresa May's party might lose 20 of the 330 seats it holds, with Jeremy Corbyn's Labour gaining almost 30 seats.
The pound has fallen below the $1.28 mark after a new poll predicted the Conservatives could fail to win a majority in next week's general election.
The Tories finished roughly seven points ahead of Labour in 2015, so finishing nine points ahead this year doesn't equate to much of an improvement.
The Labour leader hit back by accusing the government of offering five more years of austerity "to fund tax handouts for the wealthy few".
In a campaign speech in Teesside, she launched a renewed attack on the Labour leader, saying he would be unable to negotiate the deal with the remaining 27 member states that the United Kingdom needed.More news: Trump to announce Paris climate deal decision Thursday
A protest song branding May a liar was heading for the top of the charts on Wednesday - despite the BBC refusing to play it for fear of breaching electoral rules. Other polls in recent days predict May's majority is safe.
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