THE United Democrats are to raise a motion in the Legislative Council calling for a public referendum on Governor Mr Chris Patten's political proposals. The motion, to be raised by the UDHK's Mr Setzo Wah on April 21, will call on the Government to hold a referendum on provisions for the three-tier elections before the bills are tabled in Legco. The move was criticised last night by Chinese officials, with the deputy director of the Hongkong New China News Agency, Mr Zhang Jun-sheng, saying ''is it a joke?'' Mr Zhang said legislators had no right to discuss the affairs of the British and Chinese governments. The motion also met opposition from the Government which said Legco was the best body to decide the proposals. But UDHK chairman Mr Martin Lee Chu-ming said he was confident the motion would have the support of Meeting Point, the Co-operative Resources Centre and independent legislators. CRC convener Mr Allen Lee rejected the motion yesterday, however, saying Legco might decide on the political reform proposal within two weeks and a referendum would then be meaningless. Mr Martin Lee defended his decision to reintroduce the motion, which had been put off in October, saying it was the appropriate time to do so because sources said the Executive Council had passed the reform package.