New South Wales Farmers has hit back at supermarket giant Coles after a number of its suppliers received letters asking them to "cut costs" rather than ask for price rises for their produce.

Farmers in the state have been facing pandemic disruptions, extreme floods, skyrocketing fertiliser and fuel prices and labour costs as well as logistical difficulties.

In the letter, seen by ABC, suppliers are asked to "turn their minds to" cutting costs on the supply side rather than relying on a price rise from Coles, which may not be accepted "in full or in part".

NSW Farmers vice-president Rebecca Riordan said farmers were doing it tough.

"My production costs on my farm have doubled — they're up over 100 per cent," she said.

'Trying to screw the farmer'

The letter says the supermarket is receiving such a high volume of requests from suppliers to review their cost price that it has dedicated additional resources to deal with them.

The letter sent to suppliers by Coles makes it plain that not all requests for cost price increases will be considered or implemented, but if farmers do see savings they will be expected to pass those on to Coles.

Ms Riordan said statements like that revealed what Coles thought of farmers.

She said prices were not reflecting the fact that farmers' costs were through the roof and that the price increase that consumers were paying at the farm gate did not match production cost increases.

NSW Farmers was now calling for competition reform to address the supermarket duopoly.

"We've got a company like Coles, which is making a billion dollars a year after tax, flexing its muscle and trying to screw the farmer," Ms Riordan said.

Coles has been approached for comment.