DESPITE the release of a few high-profile political prisoners, China is continuing to crack down on all forms of political dissent, a new report by the New York-based human rights group Asia Watch reveals. The 26-page report, published today, details the cases of at least 40 non-violent dissidents who have been arrested since last May and are now facing trial for their alleged involvement in underground democracy groups. More than a dozen people were detained in Beijing itself, often without their families being notified for months on end, while other arrests occurred in Tianjin and Shenzhen, and the provinces of Anhui and Gansu. The report also provides a detailed account of the crackdown which followed the return to China and detention last year of exiled student activist Shen Tong. Nearly a dozen people in Beijing, Tianjin and Hunan province were detained after being contacted by Shen and although some have been given conditional discharges, at least five are still being held. The biggest casualty of Shen's ''summer project'', the report says, was the Hunan based All-China People's Autonomous Federation, many of whose members were arrested or fled the country. The federation is one of five underground pro-democracy groups that emerged last year. The others included: the Beijing based Liberal Democratic Party of China, which issued several statements to foreign journalists condemning the Communist Party's human rights abuses; the Free Labour Union of China, which sought to establish an independent trade union; and the Social Democratic Party, based in Lanzhou, Gansu, most of whose leaders were arrested in August last year. Perhaps the most radical group was the China Progressive Alliance, which advocated an ''underground struggle'' to ''liberate the nation and the people from the system of dictatorship, autocracy, corruption and ossification''. Asia Watch says the suppression of these groups shows that while China is liberalising economically, the Government has no intention of allowing greater political freedom. The current ''smile campaign'' involving the release of a few well known dissidents is an exercise in political cosmetics aimed primarily at the new administration in the US, the report says. ''These steps are welcome, but for the Government's 'smile' posture actually to amount to anything, it will be necessary for the authorities to go well beyond such token concessions to international opinion, and begin to make a real dent in the huge backlog of political prisoner cases,'' it says. Asia Watch spokesman Mr Robin Munro says there are still hundreds of documented cases of political prisoners. The vast majority of those in detention were workers and dissident intellectuals rather than students, Mr Munro said, and it was these cases that needed to be highlighted rather than student celebrities such as Wang Dan.