Including fuel, like-for-like sales rose 6% during the period, the retailer said in a trading update.
Total sales for the six weeks were up by 5.2%.
Although trading in the run-up to Christmas was muted, the week immediately prior to Christmas saw a record performance, it added.
It had also reduced waste and markdowns in the week following Christmas by 20% against the previous year.
For the 49 weeks to 7 January, like-for-like sales were up by 5.4% excluding fuel and by 6.3% excluding fuel. Total sales excluding fuel rose by just 0.4% during the period.
“These sales results are slightly ahead of our expectations at the time of our interim results. However, the group is in the early stages of its profit recovery and the trading environment remains highly competitive,” it warned.