Campaigning is in its final stages ahead of Thursday's Scottish, Welsh and English local elections.
Mr Brown led the final push for Labour votes in Scotland
The polls are the biggest test of public opinion since 2005's general election - and will be Tony Blair's last as Labour leader.
All of the parties have been out in force - the contest is expected to be particularly fierce between Labour and the SNP in Scotland.
Labour is also battling to regain control of the Welsh assembly.
Labour's opponents have urged voters to use Thursday's polls to issue a verdict on Tony Blair's 10 years in power.
But Mr Blair, who is expected to announce his resignation next week, has urged voters to resist the temptation to give him one final "kicking" at the ballot box.
He has warned that the SNP, which has pledged a referendum on independence, would cause "chaos and instability".
And on Friday First Minister Jack McConnell, who was joined by Home Secretary John Reid in central Glasgow, urged Scottish voters to "come home to Labour".
Labour has governed in coalition with the Lib Dems for the past four years - and Scotland's electoral system makes it difficult for one party to command an overall majority.
But, if the SNP becomes the largest party, it could force Labour out of power for the first time since devolution in 1999.
Leader Alex Salmond said Labour did "not have a divine right to rule" and pledged a healthier, and wealthier, Scotland under the SNP.
He added: "It's time for fresh thinking and a new approach to build a more successful Scotland."
Chancellor Gordon Brown - whom Mr Blair has said he expects to take over as prime minister - returned from an EU conference in Brussels to lead a last-ditch battle for Labour votes.
Senior figures from all the parties - including Mr Salmond - were also on the campaign trail for a final push.
In Wales, where Labour is fighting to regain control of the Welsh assembly, the party leaders have also been criss-crossing the country in a last bid for votes.
Labour lost its majority in 2005 after Blaenau Gwent AM Peter Law became an independent.
It still expects to be the largest party after Thursday's poll, but a combination of Plaid Cymru, the Tories and Lib Dems and independents could gain enough seats to form a ruling coalition, forcing it out of power.
Plaid Cymru also hopes to remain the largest opposition group and speculation has been rife about its likely coalition partners.
The elections will also be a test for Tory leader David Cameron
In the Commons on Wednesday, Labour MP Alun Michael warned of a "negative nexus" of nationalists and Conservatives.
But Plaid leader Ieuan Wyn Jones said the Labour vote was "in meltdown" adding: "The people of Wales have a clear choice on Thursday, four more years of the same with Labour or a change of direction with Plaid."
Labour is under pressure in English local elections too, where it is expected to lose hundreds of seats.
The poll will also be a major test of David Cameron's leadership of the Conservative Party - and his claim to be on course to win the next general election.
PARTIES DEFENDING SEATS IN ENGLISH LOCAL ELECTIONS
Lib Dem: 2419
ALL OTHER: 1277 of which:
Mebyon Kernow: 6
Source: BBC Research
The Tories will be looking in particular to pick up seats in the Midlands and North of England, where they have struggled to make an impact in recent years.
On Wednesday, Mr Cameron admitted his party also had a "real battle" ahead of it to re-establish itself in Scotland.
He told GMTV: "We got wiped out in that 1997 election.
"We only have one member of Parliament, we are hoping to build back, and we will have to build and these things do take time."
Across England, 32.8 million people will be able to vote - with seats being contested in 312 local authorities.
In some councils one third of seats will be up for election; in others, the whole council will be elected.
There are also mayoral elections in Bedford, Mansfield and Middlesbrough.
It is the biggest election in the local cycle in England, with about 10,500 council seats up for grabs.