Supermarkets have been covering up non-essential goods as Wales enters a national lockdown.
From 18:00 BST shops will be forced to close for 17 days, unless they sell essential items such as food.
First Minister Mark Drakeford has said supermarkets should also stop selling items such as clothes as a matter of “fairness” until 9 November.
But the Welsh Retail Consortium said it was “deeply disappointed” with the “ill-conceived policy”.
Retailers have said the rules are confusing as they have not been given any definition of what is essential.
By law, clothing and homeware stores, and garden centres, will have to close during the national lockdown, while supermarkets, pharmacies and hardware stores can remain open.
On Thursday, the Welsh Government said that supermarkets would be told not to sell non-essential goods, like clothes, toys, decorations and electrical items during the 17-day firebreak.
Plastic covering was seen placed over pillows and cat baskets in Asda in Coryton, Cardiff.
The company said it had been given “little time to implement these changes or clarity on what is deemed ‘essential'” and had “expressed our deep concerns about the implications for customers accessing products they genuinely need”.
‘Dearth of clarity’
Tesco said it would work “incredibly hard” to comply with the Welsh Government’s rules, while Sainsbury’s said it was “working around the clock to put changes in place”.
The Welsh Retail Consortium said: “In spite of the dearth of government clarity, our members’ focus now will be on equipping hard-working colleagues with as much information as possible given the undoubted uncertainty and complexity that has been caused by this decision.”