WHARF Cable television network is losing up to 25 per cent of its subscribers and the number of households that have signed up for the service may be far less than the company claims. Actual subscribers total 65,000 compared to the figure of 100,000 claimed by the company spokesman yesterday, said authoritative sources at Wharf Cable. Customers are rejecting the pay-TV service at an average rate of 25 per cent in the New Territories and 13 per cent in Kowloon, the Sunday Morning Post was told. ''There is a problem with positioning the product in the market and the challenge is to reduce the churn factor,'' a senior Wharf Cable source said. ''We have to realise that our initial forecasts were far too optimistic. We have about half the number of subscribers we originally planned,'' the source added. ''Churn'' data, or the rate at which subscribers give up the service, has a delay of about three months because Wharf offers the second month rental free of charge. ''The fact is that cable TV is too young to have a statistically recognised churn factor which is normally calculated on an annual basis in the industry,'' company spokesman Benny Chan said. Wharf had more success getting subscribers in Kowloon because the community was older and more settled which made it easier to negotiate with the individual building committees to fit the cable service, said the source. Over 700,000 homes have been wired up for cable TV, which should increase to 1.2 million by the end of the year, said Mr Chan. The cable network was achieving a 10 per cent ''penetration rate'' of those households which were now wired for the service, said a source. This figure compared to an average penetration figure of about 60 per cent in the United States. Since June the company has run an intensive advertising campaign promoting the service but a securities analyst covering the Wharf stock said it had missed the mark.