THE United Democrats of Hongkong (UDHK) will tighten its code of conduct following the arrest of three of its district board members for illegal gambling. UDHK vice-chairman (internal affairs) Albert Ho Chun-yan said last night that his party would review rules governing the conduct of members. He said the party was concerned because the matter affected the UDHK's reputation and credibility. But disciplinary action against the trio would be considered only after a court hearing, if any. The trio - Christopher Chu Cho-yan, Shung King-fai and Willy Ng Wai-cho - are elected Tuen Mun District Board members. They, and district board colleague So Shiu-shing, were among 40 people arrested playing mahjong and cards in a building in Sam Shing Street, Tuen Mun, on Tuesday. All were released on bail of $1,000 and will have to wait until July 27 to find out if they will be prosecuted. Chu and So said yesterday they were innocent and had gone to play mahjong at a club in the building, having made sure the club had a licence. Police said the licence was not for playing mahjong or cards. So said: ''We just wanted to take the opportunity to get to know each other better and to facilitate co-operation on social issues. ''We were only playing for fun.'' Ng and Shung, who is a member of the Tuen Mun Fight Crime Committee and vice-chairman of the UDHK New Territories West branch, were not available for comment. Mr Ho said that if the three were charged, it would be the third time UDHK politicians had been involved with the courts. Wong Tai Sin District Board member Andrew To Kwan-hang was yesterday convicted of unlawful assembly. Wan Chai District Board member Steven Pak Sum was acquitted last year of election fraud and later quit the party.