Legislators have promised an investigation into claims that police blocked the formation of a pro-democracy group. Officers allegedly rejected activist Leung Kwok-hung's application to register a group called Forget Not June Fourth because of a line in the group's constitution calling for the end of one-party rule on the mainland. Mr Leung submitted his application in January. He said he had applied to register another group which did not touch on one-party rule and this was approved in two weeks. 'It is a political suppression. The police have denied our rights to form groups,' said Mr Leung, who petitioned legislators yesterday with fellow activist Lau Shan-ching. They were received by Emily Lau Wai-hing of The Frontier and Democrats Lau Chin-shek and James To Kun-sun. The legislators said it was a serious case and promised a thorough investigation. A police spokesman last night would not comment.