'When I got involved with the anti-war movement - which included calls for more social change - I felt, for the first time, I was involved in something that was both important and that really spoke to me.'

Despite having poor English language skills and no social science background, Kwong was accepted into Columbia's School of International Affairs.

But in 1969, as the Asian-American movement was forming, Kwong dropped out of graduate school and joined other politicised Chinese-Americans to become community activists in New York's Chinatown.

He lived and worked as a community organiser among the area's largely working- class Chinese, setting up self-help programmes, a food co-operative, an English language school, an independent restaurant union and a grass roots political party committee.

The work wasn't easy. 'I didn't speak any Cantonese and in those days the Cantonese dominated Chinatown, so I couldn't communicate with the restaurant workers,' he says.

'And often the workers frustrated us because, although they were unhappy about their services, they weren't necessarily willing to agitate or organise to address these conditions. In the same way, they were anti-communist, but happy to see the changes in mainland China. It was hard to know how to deal with that contradictory duality.'

Wanting to probe Chinatown's social and political complexities, Kwong returned to Columbia, this time to study for a PhD in political science while continuing to live and organise in Chinatown. His first book, Chinatown, New York: Labor and Politics (Monthly Review Press) appeared in 1979, to be followed eight years later by The New Chinatown (New Press), a book that's now considered a classic in its field and a must-read for anyone who wants to understand Chinese communities in New York and other US cities.

Kwong's interest in the plight of Chinese workers in the US led to his third book, Forbidden Workers: Illegal Chinese Immigrants and American Labour (New Press) and his becoming an expert on Chinese illegal immigration.

This October, he'll publish Chinese Americans: A History in the Making, which he wrote with his wife, writer and translator Dusanka Miscevic.

Although the path of leftist activism is taken by a minority of US-born Chinese, for a foreign-born Chinese to do so is almost unheard of. Asked what compelled him to do it, he responds with an answer solidly rooted in Chinese tradition. 'I was an avid reader of the Chinese classics, books like The Monkey King, The Outlaws of the Marsh and The Romance of the Three Kingdoms. If there's any one idea shared by these novels it's a revulsion against injustices perpetrated against the weak and the idea that the injustice has to be corrected.'

Kwong - the son of a disillusioned nationalist central bank official who became a professor of English at Fudan University before finally departing for Taiwan - says his belief that the writer's job is to defend the underdog is in the Chinese tradition. 'Chinese intellectuals have always felt it's their responsibility to criticise society,' he says.

Although he spent his youth in Taiwan, Kwong was born in Chonqing. He came back to China for the first time in 1980 when he was invited by Fudan University to teach political science. He's returned many times since, often to work on articles or film projects - such as the 2002 documentary To Have and Have Not about conditions for workers.

Kwong's next book will have nothing to do with Chinese labour or politics. It will be a family memoir delving into his father's tangled personal life, including his first marriage to an American woman that resulted in the birth of Kwong's mixed-race half-brother who grew up in China while Kwong was raised in Taiwan.

The project will be a change of direction, he says. 'I've always been an external-oriented person. Partly that has to do with growing up in a dysfunctional family, so now I'll direct my attention inward to rediscovering and reconciling the past.'