Caterers are continuing to con consumers by serving chicken containing large amounts of water, pork and beef.
Some chicken contained beef and pork
An investigation by the Food Standards Agency has found thousands of tonnes of chicken are still being "bulked up" to make them look bigger than they are.
While the practice is not illegal, misleading or inaccurate labels are. It also raises the prospect that some people who do not eat beef or pork for religious reasons are eating it inadvertently.
In addition, it suggests consumers are paying too much for chicken that is being marketed as 'fillet' or 'breast' when it is not.
The findings come 15 months after the FSA first reported that caterers were selling "bulked-up" chicken.
As part of a follow up exercise, Hull Trading Standards officials examined 25 samples of chicken taken from wholesalers and one manufacturing site across the UK.
The chicken had been processed in either one UK plant or plants in Belgium or Holland.
They found that 15 of these samples claimed to contain more chicken meat than they actually had.
What is even more unacceptable is the total disregard as to how offensive this is to Muslim communities who may be eating food which is forbidden by their religious beliefs
Twelve samples contained 'non-chicken' DNA, such as pork or beef. Eleven of these were wrongly labelled as Halal and suitable for Muslims.
Eighteen of the 25 samples were described as chicken breast or fillet when they were not. Only chicken with no added ingredients should be described in this way.
The FSA said it had passed its findings onto trading standards officers, who will consider whether to take legal action against the firms involved.
It said it was determined to bring what it called a "consumer con" to an end.
"We know that in some cases consumers are not always getting what they pay for and the Food Standards Agency is determined to stamp this out," said David Statham, its director of enforcement.
"What is even more unacceptable is the total disregard as to how offensive this is to Muslim communities who may be eating food which is forbidden by their religious beliefs."
Steve Butterworth, of the Trading Standards Institute, said: "These matters are of concern to everyone who eats chicken.
"Consumers are being misled by other meat proteins being put into these products."