GANGTOK, Oct. 10: The four Opposition parties of the state ~ Congress, BJP, CPI-M and Sikkim Himali Rajya Parishad ~ have requested the State Election Commission to foil the ruling Sikkim Democratic Front's alleged bid to rig the upcoming panchayat polls in the state. The Opposition parties, meanwhile, have appreciated the Election Commission's decision to replace the returning officer of Soreng sub-division in West Sikkim during filing of nomination papers. "We believe that by doing so the EC has proved its credibility. We expect the EC officials to take action on several representations submitted by the Opposition parties and individuals," a letter sent to the EC by the Opposition parties, read. The Opposition leaders have suggested the EC to strictly implement the election code of conduct. "We have noticed that still many ministers, MLAs, chairpersons and advisors are using government vehicles for electioneering," they said. The Opposition parties have urged the EC to prevent the SDF from defacing buildings, walls and trees in the name of electioneering. They have also criticised the SDF for publicising the recent 40 per cent seat allotment to women in the panchayat polls through banners. The Opposition leaders have urged the EC to remove such banners.