Southlake Marketplace has a hub in Cooranbong and four other food banks, which usually have about 350 regular customers and another 250 who occasionally access the free and discounted food and other everyday items, such as toiletries.

This week the service has had about 800 people through its doors.

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"We went through 1.8 tonnes of pasta this week," said Southlake Marketplace's founder Christine Mastello. "We went through 300 bags of rice. We went through 400 2-litre [cartons of] milk."

"This has been our biggest week ever over the five sites," said the service's committee chairperson, Kerriann Dunn.

Many of the new faces, Ms Mastello said, were families.

"They have been saying they can't buy food from their normal outlets and they can't feed their children," she said. "Their husband has been put off from work or they've been put off from work, or they've got less hours at work."

While most customers had been considerate and appreciative, Ms Mastello and her volunteers said they had also confronted some ugly aspects of human behaviour.

"It's gone from one extreme to the other," said the service's vice chairperson, Vicky Carr, "from the bushfires to 'I'm going to get that toilet paper before you'."

Christine Mastello said one man swore at her and was physically aggressive when she told him to use the hand sanitiser at the entrance. More had barged past in Cooranbong, refusing to use the sanitiser. A few others had demanded to buy more products than the limits allowed.

Ms Mastello said she had not seen the clients who were behaving like that before. Southlake Marketplace was now planning to restrict access to existing customers or those who had been referred to the service.

"We have to look after the people we've always looked after," Ms Mastello said.

The volunteers said there had also been a few instances of theft. On Wednesday, hundreds of emergency toiletries packs, earmarked for homeless women, were stolen from a pallet that had just been delivered.

From next week, Ms Mastello said, new limits were being put in place. The service was assembling "essential food packs", including bread, tinned food, soup, long-life milk and fruit and vegetables, "to make sure we can continue to supply the most vulnerable in our society." Those packs will be limited to one per household.

Christine Mastello said as demand grew, supplies were thinning, with food donations drying up. For example, bread came from food rescue organisation SecondBite.

"We normally get 400 kilograms of bread donated, and we got 40 kilograms this week," she said.

State Member for Lake Macquarie Greg Piper said he would look at how to further assist those services who in turn help the vulnerable, especially at this time.

"I'll be talking to the government about what we can do in supporting these small food banks and other organisations, because they're so well connected to the community, and they get targetted assistance into the community," he said.

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