FOOD processors are opposing a push by Opposition Senators to strengthen country-of-origin labelling laws.

Peak grocery and beverage bodies and leading processors say food companies would face constant label changes and higher costs if the proposals were to be implemented.

The National Farmers Federation, while supporting better labelling laws, has also warned about extra labelling costs being passed back to farmers.

But vegetable peak body AUSVEG backed the move and rejected the cost claims, as did AusBuy, a body representing more than 100 Australian-owned manufacturers.

The comments came at a Senate inquiry last week into "truth in labelling'' legislation put forward by independent Senator Nick Xenophon and the Greens, and supported by Nationals Senator Barnaby Joyce.

Under the move, the Made in Australia label would be restricted to produce 100-per-cent sourced from and manufactured in Australia, rather than the present requirement for at least 50-per-cent value added in Australia.

Senator Joyce is also pushing for all food labels to carry two gold-coloured pie charts showing the proportion sourced and manufactured locally.

Australian Food and Grocery Council chief executive Kate Carnell said the proposed Bill would rule out Made in Australia labelling for products which sourced a small but key ingredient from overseas.

These included local hams which used imported brine not available in Australia, and meat pies which might be all local except for imported pepper, she said.

Ms Carnell said the industry was in a position to use bar-code technology to allow consumers to access a whole range of specific information on a product, rather than putting everything on the label.

Senator Joyce said his "diagrammatic representation of proportionality'' would address that problem by allowing consumers to see at a glance how much of the product was local.

Nestle's director of corporate and external relations, Peter Kelly, said his company was concerned about the costs of changing labels when seasonal conditions meant ingredients had to be imported, as happened recently for the oats used in Uncle Toby's oats.

But Senator Joyce said a four-yearly average or a 12-monthly rolling average could be used for the colour charts on food labels.

AUSVEG chief executive Richard Mulcahy said the cost argument by processors was just a "smokescreen'' for not really wanting consumers to know where food products came from.

He said food labels should also be required to identify the origin of imported ingredients because of legitimate consumer concerns about the food quality and safety of some countries.