Figures from accountancy firm BDO showed the sales surge hoped for by many shops failed to materialise in the crucial trading period, with like-for-like sales, excluding online trade, dropping by as much as 6.7% in the week to December 22.
Even a 3.5% surge in the week to December 29 failed to boost the overall performance for the month, which compared with a 1.9% rise the previous December.
BDO said: "Following on from what was a solid month of trading in November, many retailers will have been left disappointed by a month of lacklustre consumer demand in the crucial Christmas trading period."
"Pent-up demand was expected to play a larger role as we moved closer to Christmas day but in reality it never fully took hold," it added.
It comes as one of the remaining HMV stores, in Edinburgh's Fort Kinnaird Park, continues its closing-down sale.
The music firm entered administration a year ago and dozens of its branches have closed down since then. A total of 141 branches were bought by restructuring firm Hilco.
BDO said bad weather amid the pre-Christmas storms hit trading for many, with fashion sales in particular suffering, down 4.6% last month.
But the data showed another stellar Christmas for online sales, with non-store sales leaping 31.1%, rising to growth of 55.7% in the week before Christmas.