Graphic: the election battlegrounds

Voting has started in the knife-edge battle to become Mayor of London and for 4,000 local council seats nationwide, as Gordon Brown braces himself for Labour's worst showing nationally since the 1970s.

As Ken Livingstone and Boris Johnson cast their ballots in the mayoral poll - with opinion polls showing the Conservative fractionally ahead - Labour councillors all over the country held their breath for a national backlash against the Prime Minister, with Mr Brown's party well behind in the polls.

As Londoners flocked to polling stations, with the highest turnout predicted for a mayoral election, Mr Livingstone voted near his home in Cricklewood this morning while Mr Johnson visited a polling station in Islington, accompanied by his wife Marina.

Brian Paddick, the former police officer-turned-Liberal Democrat candidate cast his vote in Vauxhall. Mr Livingstone yesterday called on Lib Dem voters to case their second-preference votes for him, claiming they could be crucial in deciding the outcome of a tight poll.

The stakes in London could not be higher, with the winner being placed in charge of an £11.3billion budget to run public transport - much of which requires modernisation - police and fire services and promote the capital's economy. The elected mayor will also act as London's figurehead in the build-up to the Olympic Games.

Amid increasingly bitter campaigning in London on the eve of the election, Mr Livingstone tried to play on public fears that Mr Johnson lacked sufficient experience and was too gaffe-prone. He launched a campaign describing the Tory candidate as a "joke" and "celebrity" politician incapable of governing effectively.

While the London mayoral poll is too close to call, elsewhere in England and Wales Labour seemed poised for a hammering in local council elections, in which some 4,000 seats on 160 councils are at stake.

Labour strategists fear that the party could record its lowest share of the vote since the 1970s, falling as low as 25% and finishing third behind the Tories and Liberal Democrats. The Conservatives expect to secure more than 40%, with strong gains in northern England.

The Prime Minister is already planning an aggressive "relaunch" campaign, with new policies, a contrite and listening tone and a fresh attempt to expose divisions with the Conservatives, party sources said. His closest advisers were drawing up plans last night to limit the damage.

In particular, Mr Brown is planning to unveil a draft Queen’s Speech at the end of this month to show that he is not running out of steam. It is expected to include measures on welfare, education reforms and involving the community in tackling crime.

Mr Brown yesterday tried to show himself to be a listening politician, when he admitted his policy to abolish the 10p tax rate - unveiled in his last budget as Chancellor - had been misjudged and that the errors had now been corrected by subsequent policy changes.

"We made two mistakes. We didn’t cover as well as we should that group of low-paid workers who don’t get the working tax credits and we weren’t able to help the 60 to 64-year-olds who didn’t get the pensioner’s tax allowance," he said.

He said that he was listening and learning as Prime Minister. He added: "The problem was quite specific. We had dealt with this very, very major tax reform. We hadn’t done enough for these two smaller groups."

Asked whether a change in government was necessary from time to time, Mr Brown replied: "I think governments need to refresh themselves." He added that he was making the "right long-term decisions".

The Prime Minister, however, aimed to show he was a man of conviction - countering Tory jibes of dithering and indecision - by pledging to stick to his guns over the controversial plans to extend the pre-charge detention of terror suspects from 28 to 42 days.

Ahead of today's poll, however, the Conservatives were trying to play down expectations by insisting that, because Labour did poorly in the corresponding elections four years ago, the scope for big Tory gains in terms of seats was limited.

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