One in every ten working people in Bolton owes his job to the Labor government." Ann Taylor, her long, wavy hair swirling in the brisk wind, reminded the 50 factory workers leaning against the grimy railroad viaduct.

In the glass-strewn vacant lot outside the J. Doyle Metal Merchants workyard, watching blonde Taylor and balding David Young, Bolton's two members of Parliament, argue the Labor Party's case were reporters from The Washington Post and The New York Times.

The Labor government's Cabinet minister for employment. Albert Booth, also was on hand. A Wall Street Journal correspondent had been by recently, as well as reporters from Britain's national newspapers. A British commercial television crew has been broadcasting a series of programs from Bolton in which nearly 500 local residents question important national figures on key election issues.

Prime Minister James Callaghan spoke from the town hall steps a week ago. Former prime minister Harold Wilson toured the local Labor Party clubs with Taylor and Young last night. Conservative Party leader Margaret Thatcher stops in Bolton next week on the last major trip of her campaign.

Why has Bolton, a city of less than 200,000 people overshadowed by sprawling Manchester less than 20 miles away, become such an important battleground in the campaign for Britain's May 3 national election?

Bolton is an unusually reliable barometer of Britain's political mood. The Bolton East seat being defended by Young has been won by the party winning control of Parliament in the last nine elections since 1950.

Young and Taylor were elected in 1974 when the Labor Party gained a small majority nationwide, making them particularly vulnerable to a national swing to the Conservatives indicated in pre-election public opinion polls. Special polling here shows that opinions of Bolton voters about political parties, their leaders and the issues in this campaign almost exactly match voters' attitudes nationally.

Bolton is Britain in miniature. The huge red brick factories from its hey-day as a textile center are gradually giving way to engineering plants on the city's outskirts. Rows of Victorian rowhouses are being demolished downtown, while suburban subdivisions for commuters to Machester are going up alongside farms on the green hillsides surrounding the industrial valley.