Morrisons saw total sales down 0.4% in the 13 weeks to 28 October 2012, as fragile consumer confidence continued to take its toll.
Like-for-like sales were down 2.1% (excluding fuel).
The retailer said consistently high levels of promotional activity in the market had also had a negative effect, with sales lower than anticipated.
However, Morrisons said it was making good progress delivering strategic initiatives, which would provide a solid foundation for future growth.
During the third quarter it introduced its Fresh Market format to a further 35 stores, and said it was on track to meet its target of extending the format to 100 stores by the end of this fiscal year.