Questions have been raised about the credibility of an anti-Occupy Central group's plan to collect signatures from those who oppose the civil disobedience movement after it admitted there were no measures in place to prevent repeat signatures. The Alliance for Peace and Democracy hopes to collect 800,000 signatures to outnumber the 780,000 people who voted in the pro-democracy movement's unofficial referendum last month on reform options for the 2017 chief executive election. "We want to find out how many people object to Occupy Central and want to avoid chaos," group spokesman Robert Chow Yung said yesterday. Chow, a former RTHK radio host, said signatures would also be accepted from people aged under 18, tourists, foreign domestic helpers and those in Hong Kong on working visas. "I believe these people should also have a say on how they want the city to be," he said. There is no measure in place to prevent repeat signatures as people who sign will be asked for only the letter and first four digits of their ID cards. "We can only ask people to exercise self-respect [and not sign more than once]," Chow said. At least 11 stations will be set up - mostly at the Federation of Trade Unions' branch offices - from July 19 to August 17 to collect signatures against Occupy Central. Signatures can also be submitted online from August 2. Occupy Central plans to rally protesters to blockade Central district if the Hong Kong government fails to come up with a satisfactory plan to implement universal suffrage for the 2017 chief executive election. The movement's co-organiser Dr Chan Kin-man said he was disappointed in the alliance's plan. "Their system won't have the slightest credibility," he said. "I thought they would come up with something much stronger … since they attacked our referendum so vigorously." Meanwhile, Tourism Board chairman Peter Lam Kin-ngok warned that Occupy Central could harm tourism in the city. The board's overseas officers had been receiving enquiries from would-be visitors about the movement, he added. Also yesterday, Police Commissioner Andy Tsang Wai-hung dismissed as "totally groundless" allegations that plain-clothes officers had incited violence at recent mass rallies. "In light of protesters' recent violent attempts to barge into the Legislative Council building and the repeated discovery of sharp objects on demonstrators, there was a need for us to deploy plain-clothes officers," he said.