JARDINE Fleming Unit Trusts is closing its doors for three months on new retail investors wishing to open accounts with the fund management house to avoid possible paperwork bottlenecks in the future. The company stressed yesterday that the unprecedented move did not affect current unit holders, who can still invest new money in or redeem money from its funds. Director Dudley Howard said yesterday the cap on new investors was due to the success of the group in attracting new account holders last year. The group expects the suspension to be temporary, lasting up to three months. The group's banking, securities and institutional investment activities are not affected. ''We had a phenomenal year, we saw 10,000 new accounts opened in December alone,'' Mr Howard said. ''Given our commitment to our current unit holders we cannot go on blindly with this kind of growth without taking action to avoid potential problems in the future,'' he said. Competitors said yesterday JF might be suffering from new investor indigestion and was taking prudent action to cope with the paper work new small account holders brought with them. The company expanded its shop-front unit trust centre last summer. Last year it saw its account holder base rise from 26,000 to 60,000 and the total of funds under management from the retail sector climb from US$1.2 billion to $4.2 billion. Its total funds under management amounted to $18 billion. A victim of its own success, JF has been trying to cope with growing business at the unit trust centre and for the new master account service. Its fund telephone service saw calls rise from 500 a week to 29,000, when 16 more lines were added. Mr Howard said the firm, having built up its business in the retail unit trust industry, did not want to throw away its reputation as a client service provider by taking on more account holders than it could cope with. At Fidelity Investment, marketing director Richard Wastcoat said: ''We also have had a huge growth in our business last year and we would be the first to admit that this growth stretched our administration. ''We have had a few hiccups and we hope that the clients have been sympathetic. We are okay now.'' Other competitors said JF had seen a major increase in business from new small retail investors who tended to move their funds around quickly. Their funds have been highly geared, compared with competitors, and the suspension in new business acquisition was a precaution against further influxes of volatile hot money. ''The action might also be an indication that JF is concerned about the state of the markets and is trying to avoid any potential for a dramatic shift in retail money from becoming a crisis,'' said another competitor. ''I notice they did not cap things when the markets were roaring ahead in early January,'' the competitor added. In marketing terms, many of JF's competitors have tended to focus on income and regional market investors which have in the past been less prone to rapidly shifting their money compared with investors who chased high-performing funds in specialist niche sectors, such as smaller companies and single country funds. Last year the group saw five of its funds reach returns of more than 200 per cent. In the 11 months to November last year, the unit trust industry saw gross sales of US$3.8 billion, which was a record. Net sales - gross sales minus redemptions - were only $52.77 million in November compared with $205.23 million in October. But the figure easily eclipsed net sales in November 1992 which totalled only $5.5 million. It was the 18th consecutive month where there were net sales.