The properties of scintillating plastic fibres that are relevant for application in hadron calorimeters are investigated with a method based on excitation by a pulsed ultraviolet laser. We measured the angular distribution and the spectral composition of the exiting light as a function of the distance that the light had to travel. The results provide information on the details of the light attenuation process. It turns out that the uniformity of the response can be improved considerably if filters and mirrors are applied, to a level where the contribution of systematic effects to the shower energy measurement is negligibly small. Measurements of the signal speed indicate that the fibres are sufficiently fast to handle 100 MHz event rates.