Payment times from supermarkets to suppliers have stabilised in recent years according to new research by RSM Tenon, but its head of agrifood Duncan Swift has warned the picture is ­muddied.

Using data from retailer accounts from 2005 to 2009/10, the research revealed the number of days taken by major multiples to settle invoices had remained relatively flat, at about 38 to 39 days. Only Tesco showed a gradual increase in time-to-pay over the past three years, but it still settled more quickly on average than its peers.

However, Swift warned, volume discount rebates, pay-me-early schemes and supply payment schemes flattered creditor profiles.

"There are several explanations as to why the weighted average is flat when suppliers are complaining they are having extended terms," he said. "But unless a supermarket is willing to disclose more information throughout its dealings in a year, we're not going to be able to extract their true creditor profile."