May retail sales fell at their sharpest rate in more than a year but retailers remain positive forecasting sales growth next month.

The CBI Distributive Trades Survey, which questioned 69 retailing firms, showed May sales fell at their steepest rate since January 2012. This defied expectations last month that the decline would be “much slower”.

The CBI said that this shows that the retail sector has “persistently” weakened during 2013 as the results follow a disappointing April when Easter sales were lower than expected.

The month’s performance was dragged down as food sales growth slowed against last month with sales staying flat in May. Sales fell across most other categories, including clothing and footwear. But sales of furniture and carpets and recreational goods all increased.

Retailers said overall sales volumes for the time of year were below average. Orders fell faster than at any point since November 2011.

But they expect sales to rise “modestly” next month and the business situation to improve over the next quarter.

CBI Distributive Trades Survey Panel chair and Asda chief merchandising officer for food Barry Williams said: “Retail sales growth has weakened since the start of the year as households continue to feel the pinch, with wages failing to keep pace with the cost of living.”

But businesses said they are planning to scale back spending for the remainder of the year, as investment intentions are now the weakest since the start of last year.