GO:0010956

Any process that decreases the rate, frequency or extent of calcidiol 1-monooxygenase activity. Calcidiol 1-monooxygenase activity is the catalysis of the reaction: calcidiol + NADPH + H+ + O2 = calcitriol + NADP+ + H2O. [GOC:BHF, GOC:dph, GOC:tb]