The Conservative party lead over Labour has narrowed to five points, down from 15 points two weeks ago, according to an opinion poll from Ipsos MORI.
Just six days before the general election vote, the poll showed the Conservatives' share of the vote had fallen to 45 per cent, down four percentage points since the previous poll published on May 18.
Labour's share of the vote increased by six points to 40 per cent.
The poll is the latest to show a narrowing lead for the Prime Minister - who held a 24-point lead before campaigns began.
Meanwhile, the Liberal Democrats hold a total of seven points, according to the Ipsos MORI figures, published in the Evening Standard on Friday.
Theresa May's personal opinion poll ratings are also said to have fallen to their lowest yet, following a series of blows to the party's campaign.
Ms May has struggled in recent weeks after she was forced into an embarrassing U-turn over plans to reform social care in the party's manifesto.
She faced further criticism this week after she declined to take part in televised debates, sending Home Secretary Amber Rudd in her place.
A YouGov opinion poll on Wednesday showed the Conservatives' lead had fallen to a record low of three points.
Favour for Labour leader Jeremy Corbyn is said to be growing as a consequence of Ms May's proposals to scrap universal free school meals, as well as raised care costs.
Before the publication of the Tory manifesto, women were divided 49-35 for the Conservatives over Labour.
Since the row over social care came to light, the gap has closed to 45-44.
Gideon Skinner of Ipsos MORI said: “Here’s more evidence of the Conservatives’ wobbly week, with Labour improving again and the last two weeks of campaigning seeing a big hit to the Prime Minister’s personal ratings.
"But remember this is just a snapshot of a period of time, not a prediction – the Conservative vote share remains high, May is still seen as the most capable Prime Minister, and they still have the support of older people.”
The Conservative leader still held a clear lead of 50 per cent when voters were asked who would be a more "capable" Prime Minister, although that gap has also narrowed by six points since last month.
