Based on our sample of 10 095 galaxies with bulge‐disc decompositions we derive the empirical BMGC-band internal attenuation‐inclination relation for galaxy discs and their associated central bulges. Our results agree well with the independently derived dust models of Tuffs et al., leading to a direct constraint on the mean opacity of spiral discs of τ f = 3.8 ± 0.7 (central face-on BMGC-band opacity). Depending on inclination, the BMGC-band attenuation correction varies from 0.2 to 1.1 mag for discs and from 0.8 to 2.6 mag for bulges. We find that, overall, 37 per cent of all BMGC-band photons produced in discs in the nearby Universe are absorbed by dust, a figure that rises to 71 per cent for bulge photons. The severity of internal dust extinction is such that one must incorporate internal dust corrections in all optical studies of large galaxy samples. This is particularly pertinent for optical Hubble Space Telescope comparative evolutionary studies as the dust properties will also be evolving. We use the new results to revise our recent estimates of the spheroid and disc luminosity functions. The implied stellar mass densities at redshift zero are somewhat higher than our earlier estimates: ρdiscs =