Rises in energy bills have seen families' finances come under increasing pressure, a report suggests.
Utility costs have soared by 8.2% in the year to July, marking the strongest annual rise seen since August 2012, according to Asda's income tracker report.
Overall, UK households were found to be £1 a week worse off than they were a year ago, with £160-worth of discretionary income a week.
This is also £5 a week less to spend than a recent peak recorded in January 2010, as wages remain stagnant.
July also saw rising annual inflation on petrol and diesel prices. Vehicle fuels rose over the year by 2.4%, up from 1% the previous month.
An easing back on the cost of mortgage interest payments, after a mortgage price war recently broke out among lenders, has also helped to take some of the pressure off rising living costs.
Some relief for people's budgets also came from clothing prices falling as summer sales kicked in, while recreation and culture costs also fell back.
The report is compiled for Asda by the Centre for Economics and Business Research (Cebr).
Andy Clarke, Asda president and CEO, said that families are starting to feel "less gloomy" about their finances, despite the slight overall drop in disposable income.
He said: " A 'feel-good' summer has contributed to a boost in retail sales, but we can't ignore the fact that the squeeze on income growth and the rising cost of living continue to pull at consumer purse strings."