[en] Neutral Higgs bosons were searched for in the data collected by DELPHI at a centre-of-mass energy of 183 GeV, corresponding to an integrated luminosity of 54 pb^-1. The production of the lightest neutral Higgs boson with either an on-shell Z boson or a neutral pseudo-scalar Higgs boson was analysed. Lower limits at the 95% confidence level were obtained on the Higgs boson masses. The limits are 85.7 GeV/c² for the standard model Higgs boson and 74.4 GeV/c² for the scalar and 75.3 GeV/c² for the pseudo-scalar Higgs bosons as predicted by the minimal super-symmetric extension of the standard model with commonly used assumptions on the model parameters, plus the assumption that the mass of the pseudo-scalar boson is greater than 20 GeV/c². These results significantly improve the limits reached with previous data. (orig.)