Average fractions of non-prompt \Dzero and \Dplus mesons as a function of multiplicity, both normalised to the value corresponding to the \inelgtrz class, for pp collisions at $\s=13 \TeV$ in different \pt intervals and integrated in $1<\pt<24 \GeV/c$. The measurements are compared with predictions obtained with the \pythia  and \epos  event generators and the \cgc model .