THE Government was yesterday accused of practising political prosecutions when it used the Public Order Ordinance to charge three former secretary-generals of the Hongkong Federation of Students outside the New China News Agency headquarters on June 5, last year. In a petition to legislators, representatives of the 30,000-strong federation urged the Legislative Council to raise a motion to narrow the ordinance's power. They said the present ordinance could be easily abused to deprive the public rights of peaceful gathering. Federation spokesman Leung Ka-shing said after meeting four legislators Peggy Lam Pei Yu-dja, Lau Chin-shek, Simon Ip Sik-on and Tik Chi-yuen they were not satisfied with their replies. ''They did not offer us firm commitment. They only said they would look into the matter,'' he said. Three former federation secretary-generals - Andrew To Kwan-hang, Choi Yiu-cheong and Wong Ching-man - have been charged with illegal gathering under the Public Order Ordinance. Their case starts tomorrow at Eastern Court.