Britain's fourth biggest supermarket group Morrisons has warned it would take a long time to rebuild after a 35% slump in first-half profit to its lowest level in nine years underscored the scale of the challenge. 

Morrisons is engaged in a price war with rivals to stem the loss of shoppers to discounters Aldi and Lidl.

It said its turnaround plan would take time and require sustained investment after the group failed to stand out in an increasingly crowded market. 

The supermarket group has been particularly hard hit because the discounters are strong in its northern heartlands and it was late to move to into the better performing parts of the market, namely online shopping and convenience stores. 

It said today it would close 11 supermarkets. Earlier this week it agreed to sell 140 convenience stores to focus on its larger stores.

Today's results, the first to be presided over by David Potts, the ex-Tesco man who took over in March, showed a slight improvement in sales at stores open over a year, which were down by 2.4% in the second quarter.

This compared with the 2.9% drop recorded n the first quarter.

The Bradford based group, which trails market leader Tesco, Wal-Mart's Asda and Sainsbury's in annual sales, made an underlying pre-tax profit, before restructuring costs, of £141m in the six months to August 2, in line with forecasts. 

Turnover fell 5.1% and it reiterated guidance that underlying profit before tax would be higher in the second half of 2015-16 than the first.