The big supermarkets are coming under fire for not fully committing to a 10-cent-a-litre levy on milk to help drought-stricken farmers.

Agriculture Minister David Littleproud has accused Coles of only increasing the price of its own branded milk.

Wesfarmers Managing Director Rob Scott tells Ross Greenwood he’s “disappointed” by the minister’s comments.

“We felt that the minister didn’t fully understand what we were doing.

“Firstly, Coles has done an enormous amount to support the problems that our farmers are facing.”

Mr Scott says the supermarket chain has already funded over $12 million to the drought support.

“Importantly, customers have the choice… but as you know, [shoppers at] Coles are very price-focused and are trying to make their household budgets go further.”

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Coles has also announced its supermarket sales have jumped 5.1 per cent during the first quarter, as preparations continue for a vote on the chain’s proposed demerger.

A little boost from the supermarket giant’s ‘ ‘Little Shop’ campaign has helped the sales jump and offset a significant drop in fuel sales.

Mr Scott tells Ross this calendar year “we’ve seen a consistent improvement within Coles”.

“So there’s no question that momentum was building.”

With a proposed demerger on the table, Mr Scott says he “can’t see anything” that would through it off stage.