"A Conservative victory is likely to strengthen the pound considerably, as Brexit uncertainty would disappear provided that Boris Johnson gets enough of a majority to see his deal through Parliament", said Hamish Muress, senior currency strategist at OFX.
Two weeks ago it had forecast a majority of 68.
This means that Britain could end up with a bigger Conservative majority or another hung parliament when voters go to the polls on Thursday for the general election.
However, it warned the margin of error - together with the unknown impact of tactical voting - meant a hung parliament was still possible, as was a larger Tory majority.
Chris Curtis, YouGov's political research manager, said: "The margins are extremely tight and small swings in a small number of seats, perhaps from tactical voting and a continuation of Labour's recent upward trend, means we can't now rule out a hung parliament".
The pollsters interviewed approximately 100,000 panellists over the past seven days.
That message, he said, is that "we will protect the NHS", he will not do "secret deals" with the U.S. and will be truthful on Brexit - unlike the current Government.
In a bid to ram home his core message, Johnson ploughed a British flag-themed digger, marked "Get Brexit done", through a styrofoam wall with "gridlock" written on it.
Party leader Corbyn is set to address rallies in the northeast of England and London on Wednesday ahead of polls opening for the general election on Thursday morning. "I've come here with a message of hope".
"We will put money in your pocket because you deserve it".
The veteran socialist is planning a vast programme of public service spending and nationalisation, plus another referendum on Brexit, pitting a softer version than Johnson's against staying in the EU.
However, a number of Labour-held seats in those areas are still projected to go to the Conservatives.
Focaldata predicted that the Conservatives would win 337 seats in the 650-seat parliament, followed by Labour on 235, the Scottish National Party with 41, and the Liberal Democrats with 14 based on its forecasting model and recent polling data.
He also seized the opportunity to mock the Prime Minister, who had earlier entered a fridge while being pursued by an inquisitive reporter. "We have one more day left to do it", she said. "If Britain votes tactically on Polling Day - and these results suggest this could happen - then Boris cannot be confident of a majority to deliver his half-baked Brexit", said Miller.
Meanwhile in Northern Ireland, which returns 18 seats, the province's five major parties clashed over Brexit in a televised debate late Tuesday.
Northern Ireland's Democratic Unionists played a key role in the last parliament, propping up the minority Conservatives.