Serendipitous stellar occultation technique provides a powerful and unique tool to probe the outer Solar system matter, e.g. Kuiper disc and Oort cloud. We present the results of a serendipitous occultation observation campaign carried out with ULTRACAM, mounted on the ESO-VLT telescope, during 2005 May 17–20. The data are processed using the variability index (VI) method modified. The two-colour data set and the VI method allow searching for occulting objects in term of their distance (50, 200 and 5000 au). The analysis of ∼34 star-hours provide a working data set for assessing an instrumental approach to search for occultation events by trans-Neptunian objects. We performed recovery tests by implanting synthetic profiles in the data and defining the size of detectable objects to achieve a detection rate of 100 per cent. We propose a Fast Multi-Object Photometer (F-MOP) mounted on a 8-m class telescope and examine its performances. Such instrumental approach from the ground is able to exploit the occultation method for the exploration of the trans-Neptunian region, with a high efficiency.