Supermarket watchdog says suppliers avoid complaining
Suppliers are still "too nervous" to complain about the behaviour of supermarkets.
On Radio 4's You and Yours, the "Groceries Code Adjudicator" Christine Tacon said no farmers had come forward for fear of losing business.
The code was set up in 2010 to make sure big supermarkets did not abuse their relations with suppliers.
While she can only react to complaints, the adjudicator can fine supermarkets hundreds of millions of pounds.
The creation of the post was first recommended by the Competition Commission in 2008 to resolve disputes between supermarkets and suppliers.
It covers the 10 biggest supermarket groups - with annual turnover of over £1bn each.
She answered criticism that compared to the massive wealth of the retailers her fines would be "a nip on the side of a rhino", saying a 1% penalty could still be £500m.
'I will find them'
Issues she said she was currently investigating included supermarkets changing the terms of deals after negotiations are complete, deductions for promotions which had been agreed in the past and failing to pay full amounts by saying deliveries had not arrived.
Asked whether few suppliers were coming forward because there was little to complain about, she said: "When I do spend time with any individual supplier or with a small group it all starts to come out.
"There are some retailers against whom I hear no complaints but generally there are quite a lot of pressures leading to breaches of the code."
She assured suppliers that she could guarantee their anonymity, saying that even if the complaint was specific the practices were so widespread across the industry single complainants couldn't be identified.
She added that countries including Portugal, Ireland and Norway were all considering the creation of a UK-style Groceries Adjudicator.
Retail analysts at Cantor Fitzgerald had suggested big retailers were readily breaching the code while the role was new, in the hope they would escape the adjudicator's notice.
She said: "Breaches since 25 June can be investigated, so if anything's going on now I can still come and I will find them."