Between March 23 and June 21 of this year, a Mexican affiliate of the American-based Kirkwood Corporation, which produces electrical components for appliancemakers such as Philips, Sunbeam, and Braun, fired roughly three-fifths of its workers at a component plant in Mexico City. The reason? Like more than 100 workers fired last year at G.E. and Honeywell plants in Mexico, and six others discharged at the Sony Corporation's maquiladora facility in Nuevo Laredo, the Kirkwood workers were sacked for trying to organize an independent union - a fundamental right in Mexico's Constitution but routinely denied in the maquiladoras. The absence of strong, independent unions - keeping wages low and workers compliant - is one of the chief attractions for American multinationals that shift their operations to Mexico. Such moves have accelerated since the December 1994 devaluation of the Mexican peso, which slashed labor costs by roughly 50 percent. ''The maquiladora industry,'' says the Ciemex-WEFA economic forecasting group, ''will experience a boom in 1995-96.... As many as 160 additional plants will set up operations to take advantage of reduced operating costs.'' US-affiliated firms take a lead in keeping wages low and workers powerless. ''US companies that operate in Mexico,'' says Ed Feigen, who monitors US multinationals in Mexico for the AFL-CIO, ''are on the cutting edge of driving down wages and undermining unions. They're cleaner than sweatshops, but these plants do not pay a livable wage ....'' A case in point is the Kirkwood-affiliated plant in Mexico City. Most workers there - as at Sony, G.E., and Honeywell - are women. In late 1994, these women began complaining that the plant's lunchroom and toilets were filthy and that security guards, who frisk employees at the plant's gates, engaged in sexual harassment. The workers hoped to alter these conditions and to stanch the drastic decline in their wages precipitated by the peso devaluation by forming an independent union. Virginia Vallegas Chimal, a Kirkwood worker earning 30 pesos a day - the equivalent of $10 before the devaluation, $5 afterward - explained: ''With this salary, it is impossible to live. You're half-fed ... I have to stretch what I earn to make miracles.'' Ms. Vallegas is no longer getting by. Like roughly 150 others, she was fired after refusing to pledge allegiance to the Confederation of Workers and Peasants of the State of Mexico (COCEM), a pro-business union with close ties to the ruling government party. On June 21, after Vallegas and her colleagues were dismissed, COCEM won a suspect election granting it the right to ''represent'' Kirkwood workers. Theoretically, Mexican Boards of Conciliation and Arbitration exist so workers like those at Kirkwood can organize independently. But these boards bend over backward to serve the interests of business and government. ''If you're an independent union, that will push up wages and hurt foreign investment,'' says Mr. Feigen, ''the Board simply will not grant you recognition and will not authorize strikes.'' Not much more is granted by the National Administrative Office (NAO), the American agency that President Clinton tacked on to NAFTA to enforce labor law. The NAO's power is limited to moral suasion. In April 1994, for example, more than 200 Sony workers (mostly women) were assaulted with riot gear and fire hoses during a demonstration outside Sony's Mexican plants (they were protesting the company's attempt to stage its own union elections). The assaulted workers filed a complaint against Sony with NAO, and, on April 11 of this year, won their case. The result? US Labor Secretary Robert Reich now must ''consult'' his Mexican counterpart, Santiago Onate, about the situation - cold comfort in a country where government officials routinely favor business and stifle labor. Mexican workers are not the only victims. In the past two years, 62,000 US workers have filed claims that they lost their jobs as a result of NAFTA; 37,000 have already been certified for retraining programs by the US Department of Labor. Since the peso devaluation, such certifications have shot up from 1,200 to nearly 3,000 per month. Moreover, the US trade deficit with Mexico was a whopping $8.6 billion during the first half of 1995. DRI/McGraw Hill, a consulting firm, predicts US job loss linked to overall trade imbalances could reach 350,000 by 1997. A Kirkwood subsidiary in North Carolina, incidentally, laid off 31 workers last January because of increased import competition.