LONDON — BRITAIN'S general election battle is likely to be decided by voters in London and a handful of other large cities, judging by public opinion polls showing a swing to the opposition Labour Party in the run-up to polling day, April 9.
In the metropolis of 7 million people sprawling on either side of the River Thames, a Harris poll showed Labour two points ahead of Prime Minister John Major's Conservatives, and well placed to capture 21 key marginal constituencies from the ruling party.
A Harris spokesman said that, repeated uniformly across Britain, the 8 percent swing to Labour recorded in London would give the opposition party a slender overall majority in the 650-seat House of Commons.
But Chris Patten, Conservative Party national chairman, dismissed the Harris poll as "narrowly based" and "misleading."
One of Mr. Patten's officials noted that in the 1990 London local council elections there was an overall swing to Labour of 7 percent, but that in some places where Labour needed only a 4 percent swing, it lost.
The view that the British capital is where the April 9 outcome may largely be decided rests partly on the fact that of the 84 seats being contested there, nearly half are considered marginal.
Labour holds 23 London seats, but with more than 400,000 unemployed in the capital, among middle class as well as working class voters, Labour has high hopes of handing Conservative candidates a string of defeats.
Nowhere is the contest being fought more tensely than in Hampstead where the Labour Party challenger is Glenda Jackson, the Oscar-winning actress. Her Conservative opponent is Oliver Letwin, a youthful right-wing intellectual who helped former Prime Minister Margaret Thatcher devise the hated poll tax, which Mr. Major abolished soon after winning the premiership.
The Conservatives held Hampstead in 1987 by 2,221 votes. Mr. Letwin was chosen as his party's candidate after the sitting Conservative decided to retire.
The heart of Hampstead, with its elegant shops, neat brick facades, and Volvo station wagons, at first sight looks like Conservative country, and much of it is. But behind the curtains and pine front doors are large numbers of moderate left-wingers, concerned about the environment and inclined to believe Ms. Jackson when she suggests that it is "time for a change." Many have stuck Labour posters in their windows.
IF poll forecasts for London are accurate, four government ministers will be defeated on April 9, including David Mellor and John Maples, both high-ranking Treasury officials. Mr. Mellor's constituency of Putney, where he is defending a majority of 6,900, was cited by a Conservative official as an example of how the pollsters "have got it wrong."
The borough is run by a Conservative-led council which levied the lowest poll tax in Britain. A 7.2 percent swing to Labour would unseat Mellor, but he says he is confident of holding Putney, "because voters here know that the Conservatives have a good record and they are well aware that Labour would put up taxes."
Labour is most vulnerable where Thatcherite policies of home-ownership and self-reliance have made a deep impression. A Conservative weak point is the party's decision in the mid-1980s to abolish the Greater London Council, making London Europe's only capital without its own central administration.
Many voters speak of a void in London government, citing dirty streets, heavy traffic congestion, and a run-down public transportation system.
An official at the Conservative central office conceded that Major's plans for the administration of London have not gone down as well with voters as Labour's counter-proposals.
Labour is calling for an elected "Greater London Authority" to run the capital. The Conservatives say a cabinet subcommittee should handle London's affairs.
A Labour activist in Battersea, where the Conservatives are defending a majority of 857 votes, says the polls "show us moving ahead. Voters think our opponents have neglected London. The government is about to pay the price of its complacency."
Battersea - a mix of high-rise council estates and prim suburban houses - has been targeted by Labour ever since the party's overwhelming nationwide defeat in the 1987 general election.
In pre-Thatcher days it was a Labour stronghold, but much of it has been "gentrified" by upwardly mobile voters. On the council estates many former tenants have bought their flats.
A Battersea housewife, on the steps of a terraced house sporting venetian blinds, said: "I voted for Labour in 1983 and for the Conservatives in 1987. Major will get my vote this time."
She agreed her family had suffered "a bit" from the recession - one son was out of a job - but "I don't want Labour's high taxes."