UK families were £11 a week worse off in July 2011 than they were a year ago according to the Asda Income Tracker.
The average UK household had £166 a week of discretionary income last month, 6.4% less than a year earlier.
Annual inflation, which grew to 4.4% in July, has put significant pressure on household spending according to the grocer.
Asda president and chief executive Andy Clarke said: “”The Income Tracker spells out how tough family finances are right now. The maths is simple – the rising cost of feeding the family, getting around and increasing unemployment add up to the biggest squeeze on families since before the last recession.”