Discount food retailer Aldi has posted another jump in annual pre-tax profit as it continues to race ahead in the price war with the so-called "big four" supermarkets. Aldi reported a record £260.9m for 2013, although this represented a slowing down of growth by almost half compared to that seen the previous year.Turnover jumped 35.7% from £3.8bn to £5.2bn, while its premium products saw growth of 74% thanks to an increase in middle class shoppers.Joint managing director Matthew Barnes said: "We will remain the price leader. We have reduced prices in line with the market and we won't let rival supermarkets close the gap on Aldi."The big four have upped their efforts to battle back against discount retailers, with WM Morrison pledging a £1bn investment to cut prices in the next three years and Tesco reportedly set to introduce a "dramatic" plan of attack as they try to claw back lost market share.Last year data revealed that Aldi's market share had grown from 3.1% to 4.0%, while the most recent figures show its share has climbed to 4.8%.Looking ahead, it plans to open 54 stores this year and a further 60-65 in 2015, bringing its total number to 600."We're investing over £600m in our operations over the next two years to support this growth," Barnes said.