FILIPINOS in Hongkong are being warned against smuggling Bibles to the mainland. Hundreds of Filipinos are believed to be involved in an all-out preaching campaign on the mainland, which involves Hongkong preachers and Bible smugglers from the Philippines as well as the West. One church official, who is responsible for distributing Bibles to the Filipinos, claimed that about 500,000 copies were taken to China every year. The pastor said more than 20 churches in Hongkong with mainland links were sending Bibles over the border because of heavy demand. The Christian population was expanding quickly but few copies of the Bible were available in bookshops, he said. A Nanjing printing press of the Amity Foundation, the Bible supplier in China, produces about one million copies every year. General manager Peter Macinnis told the South China Morning Post that demand for the Bible had prompted the foundation to increase its output target by 50 per cent this year. One million copies of the Bible were produced last year and the printing press was targeting 1.5 million copies this year, he said. A director of the Mission for Filipino Migrant Workers, Cynthia Ca Tellez, said smugglers could be detained if found carrying a large number of Bibles without prior approval from China. ''The problem is we know nothing about the situation of China, some people might have been caught already but we do not know,'' she said. Miss Tellez said it was irresponsible for church officials to ask their members to become involved in illegal activities. ''Most of the Filipino domestic workers here are the sole breadwinner of the family back home, and they risk losing their job,'' she said. Benito Valeriano, a Filipino consul, said the consulate had received no reports of Filipinos being detained in China for Bible-smuggling. But he said detention was always a risk. He asked would-be smugglers to avoid breaching Chinese law. Chaplin Erik Larsen, of St John's Cathedral, warned that it was dangerous to smuggle Bibles into China. He said churches acted irresponsibly by encouraging Filipinos to smuggle Bibles as they risked losing their jobs and faced detention. According to a researcher with the Hongkong-based Chinese Churches Research Centre, identified only as Mr Wong, China's Christian population could be as high as 200 million. Official figures in 1991 claimed there were only 5.5 million. Only the Three-Self Patriotic Churches, registered under the official China Christian Council, are recognised by the Government. The three-selfs are self-supporting, self-propagating and self-governing. Family churches, common in rural areas, have not been recognised, despite the authorities' promise of freedom of religion. Mr Wong said there was an acute shortage of churches and Bibles in China. Chinese law stipulates that no printed material of pornographic or religious nature should be taken into the country. The pastor said Filipinos were involved because of their faith and eagerness to ''share the love of God'' with people in the poor regions of China. Describing it as a ''very spontaneous act'' for Christians to carry Bibles to the mainland, he said there was little risk involved as he had known of no cases of confiscation or prosecution. ''Some of them bring the Bibles at the request of churches in China while some do it voluntarily after learning of the channel in Hongkong,'' he said. ''Customs officials seldom make things difficult for Christians because many of them are Christians themselves.'' If found by customs officials, illicit copies of the Bible would be held and returned when the visitor left. Mr Macinnis said people who would like to send copies of the Bible to Christians who did not belong to the Three-Self Patriotic Churches could hand them to an association called the East Gates who would send them to Christians meeting in homes.