On the eve of Scotland's independence referendum, the fate of the United Kingdom rests on hundreds of thousands of wavering Scottish voters as opinion polls yesterday showed supporters of the 307-year union just a whisker ahead of secessionists.

In an intense final day of campaigning, leaders of both sides beseeched Scots to seize the reins of history in a vote that has divided families, friends and lovers but also electrified this country of 5.3 million.

From the remote Scottish islands of the Atlantic to the toughest city estates of Glasgow, voters will be asked today to answer 'Yes' or 'No' to the question: 'Should Scotland be an independent country?'.

Don’t let this opportunity slip through our fingers, don’t let them tell us we can’t

Four surveys – from pollsters Panelbase, Survation, Opinium and ICM – showed support for independence at 48 per cent compared with 52 per cent for the union, while a fifth, from Ipsos MORI, showed it even closer on 49 to 51 per cent.

A woman waves a Scottish Saltire at a ‘Yes’ campaign rally in Glasgow, Scotland, yesterday. Photo: Reuters

The surveys also showed as many as 600,000 voters remained undecided with just hours before polling stations were set to open at 0600 GMT today.

'Don't let this opportunity slip through our fingers. Don't let them tell us we can't. Let's do this,' Alex Salmond, Scotland's 59-year-old nationalist leader, said in an open letter to voters as he crisscrossed Scotland.

Invoking 18th-century economist Adam Smith and Scotland's greatest poet Robert Burns, Salmond implored Scots: 'Wake up on Friday morning to the first day of a better country.'

With a mix of shrewd calculation and nationalist passion, Salmond has hauled the 'Yes' campaign from far behind to within a few percentage points of winning his dream of an independent Scotland.

Facing the biggest internal threat to the United Kingdom since Ireland broke away nearly a century ago, Britain's establishment - from Prime Minister David Cameron to corporate bigwigs and pop-culture celebrities - have united in a last-ditch effort to convince Scots that the United Kingdom is 'Better Together'.

Cameron's job could be on the line if Scotland breaks away, but the 47-year-old Prime Minister has conceded that his privileged English background and Conservative politics mean he isn't the best person to win over Scots.

Electoral officials said the result of the vote is expected by breakfast time tomorrow morning, but partial results will give an indication of the trend after the count of major cities such as Glasgow are declared around 0400 GMT.