An ICM UK poll put both Labour and the Tories on 35 per cent with Ed Miliband’s party pulling back three points from the last ICM poll and the Conservatives’ score unchanged.
A final YouGov poll suggested they will both win 276 seats.
However, in Scotland, a Panelbase poll put the Nationalists on 48 per cent of the vote, ahead of Labour on 26 per cent – support which, if transferred into seats, would give the SNP a landslide, gaining all but six of the country’s 59 seats.
If that turned out to be the case, it would put First Minister Nicola Sturgeon in a potentially powerful position as the SNP would likely be the third-biggest party in Westminster.
Yesterday Ms Sturgeon made a last-ditch appeal to Labour leader Mr Miliband to talk to her if his party and the SNP can hold a majority between them.
While Ms Sturgeon has said she wants to “lock the Tories out” of Downing Street, Mr Miliband said last week he would not form a Labour government if it depended on SNP votes.
But yesterday, Ms Sturgeon said: “I don’t want David Cameron back into No10 and if there is an anti-Tory majority on Friday then I want that anti-Tory majority to come together to make sure that David Cameron is not back into Number 10.
“The SNP will use whatever influence Scotland gives us to make sure the Tories are replaced with something better, bolder and more progressive.”
When pressed on whether she would lead post-election negotiations in London for the SNP, Ms Sturgeon said: “I’m in London regardless of the outcome on Friday because it is the VE Day commemorations. I am representing the Scottish Government, but for now it is over to the Scottish people and, indeed, people across the UK.”
She added: “I have been at great pains in this campaign to say to people outside of Scotland that there is no reason to fear the SNP. You might not agree with us on everything, that is perfectly legitimate and understandable, but we want to send MPs to Westminster to play a positive and constructive role and to make Scotland’s voice heard.
“I think this could be a watershed election but we will have to wait and see how people vote.
“This is an opportunity for Scotland and whether Scotland voted Yes or No in the referendum or people have never voted SNP before, it is an opportunity to come together as a country and make our voice heard.”
If Mr Milband refuses to talk, though, she also threatened that SNP MPs would “vote down a Labour Budget” if it “continued Tory austerity”.
However, a defiant Mr Miliband has issued a last-minute personal appeal to Scottish voters to not abandon his party, with Labour trying to hold on to 41 seats north of the Border.
Over the weekend, it was revealed that Labour believes it can still win a dozen Scottish seats, which some strategists believe will be enough to put Mr Miliband into Downing Street as leader of the largest party.
In his message, Mr Miliband, who spent his final day in the north of England, said that he “holds Scotland in his heart”.
But the uncertainty was also used by Mr Cameron, who accused Mr Miliband of a “con trick” over claiming he would not do a deal with the SNP.
Raising the fear of the SNP “calling the tune” of a Labour government has become the Tories’ principal message as they try to win marginal English seats.
The Prime Minister, who visited the Scottish Borders on his final day of campaigning, made an emotional appeal to voters across the UK to back the Tories “to save the United Kingdom” from the consequences of a Labour/SNP government.
Stressing the importance of the choice voters were about to make, the PM said: “Amid all the confusion and commentary, my message is simple and clear: Britain has the chance of a strong, stable government, but only if you vote Conservative. All other options will end in chaos.
“So as you enter the voting booth, remember these simple things: you can stop Ed Miliband being held to ransom by Nicola Sturgeon and the SNP; you can ensure strong and stable government.”
He added: “You can secure our economy and the Union. You can ensure I am back at work as your Prime Minister on Friday.”
Lib Dem leader Nick Clegg also spent the final day of his campaign touring some of the 11 seats in Scotland his party hopes to hold against the SNP, which would allow them to hold the balance of power instead.
Mr Clegg claimed the Lib Dems would be the “surprise story” of election night.
With his party on 11 per cent in the UK-wide poll and just 5 per cent in Scotland, an optimistic Mr Clegg said: “At the beginning of this campaign we were written off and yet tomorrow the Liberal Democrats will be the surprise story of this general election campaign because we are going to win.
“We are going to win here against the SNP, we are going to win against Labour, we are going to win against the Conservatives.
“We are going to win because we work harder than any other political party, because what we offer the British people is in tune with their hopes and because our values are right.”
The speech was interrupted by a passing motorist shouting “Liar”, while a jogger yelled “Come on the SNP” at Lib Dem activists before Mr Clegg spoke.