Bare shelf space has been greeting customers at Woolworths stores in Parkes, Forbes and Dubbo for weeks where Mars Petcare products, including Pedigree and Whiskas, would normally sit.

Notices advised customers the products were temporarily unavailable.

"We have been experiencing supply shortages on some brands in the pet food aisle," they said.

The retailer and Mars Petcare have remained tight-lipped on the issue, but one union organiser representing workers at Mars' Wodonga factory claimed last month it was the result of a price dispute between Mars Petcare and the supermarket.

A pet owner contacted the Dubbo Daily Liberal with concerns about the issue this week.

On Tuesday Woolworths declined to comment on the cause of the supply issue, but offered assurances to customers the matter was being resolved.

"We've been working with our supplier to address recent supply shortages and stock has started returning to our shelves," a Woolworths spokesperson said.

"We have items on order and expect to see stock levels improve for customers over the next week.

"We apologise to customers for the inconvenience."

Pet owners have looked for alternatives during the shortage at the major supermarket chain.