More than two million Scots are expected to vote today in the closest fought election for a generation which will turn on the 20% of voters who are still undecided.

Two days after the 300th anniversary of the Union of the Scottish and English parliaments, tonight's result is being watched around the world as a potential breakthrough towards the end of that partnership and independence for Scotland.

Party leaders made their final pitch to voters yesterday, with the Scottish National Party arguing "It's time for change", contrasted with Labour's appeal to former supporters to "Come home".

According to Labour, the closing stages came down to an estimated one in five of likely voters who have remained undecided until the closing days, half of them having previously voted Labour.

The battle for Holyrood was reckoned to be tightening, with Labour closing the gap on the SNP in two polls published yesterday. One showed a four-point lead in the headline constituency vote, the other a two point lead.

A leading bookmakers cut the price of Labour winning most seats from 9/4 to 13/8, while pushing out the price for the SNP to 4/9 from 1/3.

However, a YouGov poll for The Daily Telegraph today gives the SNP a six-point lead over Labour in the constituency vote, with 37% against 31%, with Tories 13%, LibDems 14% and others 5%. The regional vote has the parties on SNP 32%, Labour 27%, Tories 13%, LibDems 10%, Greens 9% and others 9%.

The paper said those figures translated into seats would give the SNP 45 over Labour's 39.

SNP leader Alex Salmond took his campaign helicopter to target seats in Fife, Dundee and Aberdeen, stressing his party has never been so well-placed on the eve of an election.

Scottish Labour leader Jack McConnell was yesterday joined by Home Secretary John Reid campaigning in Glasgow, while Chancellor Gordon Brown took the message to Edinburgh voters.

Tory leader Annabel Goldie talked of scaling new heights before abseiling off a giant climbing frame in Edinburgh, while Nicol Stephen, the Scottish Liberal Democrat leader, visited Dunfermline talking of "positive policies that make a difference to families and children".

Smaller parties argued for voters to back them with their regional votes, as few are standing candidates in constituencies.

Around a tenth of the electorate has already had its chance to vote by post. Most voters will go to polling stations today and face a new electoral system for Scotland's 32 local authorities.

Using numbers and choosing candidates by order of preference, every vote will count for the first time in a Scottish election. The proportional outcome is expected to see a radical shift in the distribution of power across the nation's council chambers.