The Australian Competition and Consumer Commission is taking the Coles supermarket chain to court over its treatment of suppliers.
The ACCC says Coles has tried to squeeze $A16 million from 200 smaller suppliers through a rebate scheme.
It says some suppliers were given only a matter of days to agree to the rebates and, if the supplier refused, that suppliers would be threatened with commercial consequences.
ACCC chairman Rod Sims said the case in the federal court is part of a wider investigation of claims that supermarket chains are profiting from unfair tactics against suppliers.
Coles said it will vigorously defend the accusations.
Coles is owned by Wesfarmers. The ABC reports its shares were up 0.4 per cent at $US43.23 by 11:43am (AEST) on Monday, just below Woolworths.
Consumer New Zealand chief executive Sue Chetwin said there are parallels with investigations into the Progressive chain in New Zealand.
The Commerce Commission said it is watching the case though it points out New Zealand does not have unconscionable conduct legislation.