POLITICAL parties are set to play a more significant role in September's District Board elections than in previous years. They will back at least 400 candidates for the 346 seats. The two newcomers to full-scale polls - the Liberal Party and the Democratic Alliance for the Betterment of Hong Kong (DAB) - are prepared to field up to 100 candidates each. The United Democrats of Hong Kong (UDHK) and its pro-democracy allies are expected to support about 200 candidates. Ninety United Democrats will participate in the poll and both Meeting Point and the Association for Democracy and People's Livelihood (ADPL) have pledged to field 40 candidates. But competition within the liberal camp seems inevitable. The three main democratic groups all have similar strength in districts such as Kwai Tsing and Tuen Mun. Meeting Point chairman Anthony Cheung Bing-leung said the three liberal parties had agreed to co-ordinate candidates in the poll to avoid clashes. However, party legislator Fred Li Wah-ming doubted whether the agreement would be successful. He said that if Governor Chris Patten's political reform proposals were endorsed, board members would have the power to return 10 members to the Legislative Council. Therefore, he said, parties would have an added incentive to try their best to compete for seats. ''I think it will be a big problem for co-ordination,'' he added. Among the parties, the conservative Liberal Democratic Foundation with 40 incumbent board members may be the most generous in financing candidates. It said it could subsidise 90 per cent of election expenses as it did in the last election. Party vice-chairman Raymond Wu Wai-yung said the policy set in 1991 had not been reviewed, and the practice could be retained if members approve. The Liberal Party will not assist its members with cash but will offer other assistance. Liberal Party standing committee member Ada Wong Ying-kei said the party would provide members with resources and manpower to create a more united image. The UDHK and the DAB will grant members one-third of total election expenses and lend them another one-third. The ADPL is considering increasing financial support for its members from 20 per cent of total expenses to 40 per cent. Incumbents will enjoy a 20 per cent loan and a 20 per cent grant. The party is launching a fund-raising campaign to secure $1 million for the district board and municipal council polls. In the last elections in 1991, 370 candidates competed for 272 seats, with the UDHK as the only organised political force. The UDHK and its pro-democracy allies supported about 100 candidates.