CINEMA operators will protest to the Legislative Council today about a proposed increase in fines for allowing minors to watch category III films. The fine increase has been put forward by the Television and Entertainment Licensing Authority (TELA) in the Film Censorship (Amendment) Bill, which is to be gazetted today. It is proposed the maximum penalty for first and second offenders found guilty of allowing minors into category III films be increased from $10,000 to $50,000. The current fine for subsequent offences - $100,000 - should remain, says TELA. The Hongkong Theatres Association argues that the existing fine has proved an adequate deterrent; there have been only 21 prosecutions since the penalty was set in November 1988. It also considers it unfair that the responsibility for under-18s being stopped from seeing adult-only films falls on the cinemas. A senior TELA administration officer with the film division, Mr Alan Siu Yu-bun, said the deterrent effect of the 1988-set fines had been ''eroded by inflation''. ''A Legislative Council ad hoc committee recommended the fines should be increased to act as a sufficient deterrent for cinema operators to stop access for minors,'' Mr Siu said. In response to the cinema operators' arguments, Mr Siu said the responsibility should be with the cinemas that chose to screen category III films. ''The aim is to protect youngsters. We don't want to punish them and give them a record that would affect the rest of their lives,'' Mr Siu said. The vice-chairman of the Hongkong Theatres Association, and manager of the Full Moon cinema, Mr Wong Siu-foon, said it was almost impossible to monitor the age of all the customers who flocked to his theatre, which screens only category III films. ''In 10 minutes, 1,000 people come into the cinema. It is very hard to find out people's age, especially if they are close to 18. It is not fair to increase the penalty,'' Mr Wong said. The manager of Wan Chai's Imperial cinema, Mr Chan Him-shun, has been prosecuted 11 times under the Film Censorship Bill. He estimates the cinema has paid around $40,000 in legal fees and $6,000 in fines since May 1991. ''The problem is with the 10 am and 4 pm screenings when we have a special $20 price. Sometimes they look older than the staff even though they are under 18,'' said Mr Chan. He also called on the Government to help cinemas stop youngsters going to category III films. ''Every time they [TELA inspectors] come at the end of a screening and stand at the exit, but it is too late by then. This is not helping us to stop the problem.'' Six TELA inspectors patrol theatres that feature category III films. Since November 1988, there have been 15 successful convictions and 105 warnings. Three cases are now being considered by the courts.