The report warned that economic trends, which seemed to lift sentiment at the start of the year, are having less impact.
The latest Lloyds Bank Spending Power Index declined for the third consecutive month and is now standing at its lowest point for the year.
It said that people’s perception about their personal financial situation and Britain’s employment situation were down by two percentage points and three percentage points respectively.
At the same time, the proportion of people who say that they have disposable income dropped slightly in September, down two percentage points to four in five consumers.
Patrick Foley, chief economist at Lloyds Bank, said: “Spending power confidence continued to ease in September, providing further signs that the economic trends which lifted household sentiment through the first half of the year, such as lower inflation and improving labour market conditions, are exerting a waning influence on sentiment in the second half”.