KFS98) and thus they do not satisfy any criteria of completeness. However, all the low redshift BL Lacs in this sample have previously been imaged in the optical by us. The same procedure of analysis was performed on the NIR and optical datasets, thus allowing us to investigate the R–H colour of the host galaxies in a homogeneous manner. Properties of the observed objects are given in Table 1. In section 2, we briefly describe the observations, data reduction and the method of the analysis and refer the reader to a more thorough discussion given in KFS98. Our results are presented in section 3 and conclusions in section 4. Throughout this paper, H$_{0}$ = 50 and q$_{0}$ = 0 are used.

[llrllrrr]{}\
\
& Other name & z & V & M(B) & Date & Exp. time & FWHM\
& & & & & & (min) & (arcsec)\
\
PKS 0048–097 & OB-080 & $\geq$0.5(?) & 16.3 & – & 21/8/95 & 40 & 1.0\
PKS 0118–272 & OC-230.4 & $\geq$0.557 & 15.9 & $\leq$-26.8 & 18/8/95 & 37 & 1.0\
PKS 0521–365 & & 0.055 & 14.6 & -22.3 & 13/1/96 & 21 & 1.2\
PKS 0537–441 & & 