The Australian Food and Grocery Council says there is widespread concern about claims Woolworths is bullying suppliers.

The council's chief executive Gary Dawson said they have received complaints from a number of suppliers about Woolworths' behaviour.

Suppliers are being told to make up the difference on products that Woolworths has decided to sell at a discount, Mr Dawson said.

"Woolworths is the most profitable retailer in the world," he said.

"They're competing with retailers with much lower margins and so they are under pressure to maintain their margin and we're simply saying it's not acceptable to maintain that margin off the backs of making big claims on your suppliers on pretty dubious grounds."

The council has heard from a range of suppliers who have been asked to pay amounts ranging from $70,000 to more than $1.5 million.

They are concerned their products will be pulled off the shelves if they do not pay up, Mr Dawson said.

"For a small business being told to pay a five or six figure sum within days is quite a shock and unreasonable, and it's for a purpose where it's not clear the supplier is getting much out of it, if anything," he said.

"We have put those concerns to Woolworths. They've been put directly by companies and we would hope Woolworths would be working on addressing those concerns."

A spokesman for the supermarket giant denied the allegations and said it was not under investigation.

"Woolworths hasn't received any complaints and there's no evidence the company has acted unlawfully or inappropriately," he said.

"It's not unusual for suppliers to contribute to promotional campaigns because everyone wins."

The ABC has contacted the Australian Competition and Consumer Commission (ACCC) who said it had no comment at this stage.

Coles has already been fined for similar conduct.

The ACCC took action against Coles for unconscionable conduct and the supermarket agreed to pay a $10 million fine.