Londoners were today thought to be turning out in their biggest numbers ever for a mayoral election, as the battle between Ken Livingstone and his maverick rival Boris Johnson went right to the wire.

Early projections put voter turnout as touching the 50 per cent mark - far higher than the 37 per cent and 35 per cent turnouts in 2004 and 2000 - amid indications that the closeness of the conflict between two of British politics' most colourful characters has caught the public's imagination.

A key indication of the high turnout came at a polling station in Streatham, south London, where 85 people were reported to have voted by 9.15am, out of 1,970 in total. If traditional voting patterns were repeated during the day this would give a final poll of just under 50 per cent.

The turnout was projected to be high in advance because opinion polls have put the mayoral conflict as too close to call, while the campaign between Mr Johnson and Mr Livingstone has also been one of the most personalised and most colourful ever.

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Mr Livingstone upped the rhetoric yesterday when he described Mr Johnson, the former Spectator editor and newspaper journalist, as a "joke" and "celebrity" unable to take major political decisions.

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 in 2012.

Voting got off to a rocky start in the London borough of Barnet, however, when about 10 polling stations did not receive ballot papers until just after the election officially began, at 7am. Barnet Council said it "sincerely apologised" to voters for the slip-up.

As the London electorate cast their ballots, Labour councillors all over the country were holding their breath for a huge national backlash against the Prime Minister in local elections, in which some 4,000 seats on 160 councils were at stake.

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

Results are expected overnight for more than 100 councils, but voters elsewhere - including London - will only have the results on Friday night.

Faced with the possibility of a heavy defeat, 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 have been drawing up plans 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.

Full list of candidates to be London Mayor:

Ken Livingstone (Labour Party)

Boris Johnson (Conservative Party)

Brian Paddick (Liberal Democrats)

Sian Berry (Green Party)

Gerard Batten (UK Independence Party)

Richard Barnbrook (British National Party)

Alan Craig (Christian Peoples Alliance and Christian Party)

Lindsey German (Left List)

Winston McKenzie (Independent)

Matt O'Connor (English Democrats)

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