NSW has acquired “one of the world’s strongest mice-killing chemicals” to combat the rodents which are causing catastrophic damage in the state’s regions.

Country towns have been struggling since last year with a mouse plague that has ruined crops, damaged tonnes of stored hay and grain, infiltrated homes and caused millions of dollars of damage.

The NSW government said on Thursday it had secured 5000 litres of the anti-coagulant bromadiolone – enough to treat about 95 tonnes of grain – and would provide it for free once federal authorities approve its use.

The chemical is able to kill mice within 24 hours of its consumption.

• Related: Farmers call for mass poison program to wipe out mouse plague

The measure forms part of a $50 million government package announced last week to help farmers and regional towns suppress mice numbers.

“By securing a local supply of the chemical we ensure the NSW government is ready to roll – no waiting for overseas shipments, no immediate supply issues,” NSW Agriculture Minister Adam Marshall said in a statement.

“Experts will treat growers’ grain with bromadiolone completely free of charge to build a mice-free fortress to protect paddocks.”

Mr Marshall said the chemical should be used in conjunction with baiting.

The poison is yet to be approved for use by the Australian Pesticides and Veterinary Medicines Authority.

“This is an unprecedented plague with no blueprint on how to handle it, but we’re giving our farmers the tools they need to combat these vile vermin,” Mr Marshall said.

National Farmers’ Federation president Fiona Simson welcomed the bromadiolone acquisition but said suggestions the chemical would “napalm” the rodents were excessive.

“We can be very comfortable in Australia that we have very, very strong assessment of our chemicals that we use,” she told ABC radio on Thursday.

“We have to put our faith in the science – faith in the regulators, make sure they’re doing their job – not get too carried away with colourful language.”

Meanwhile, the prime minister has dismissed as “pretty dopey” a plea from animal activist group PETA to spare the lives of the mice.

PETA argues the mice should not be denied their right to food because of the “dangerous notion of human supremacy”, saying the government should provide a humane solution that allows the rodents to be trapped and released.

Scott Morrison said on Wednesday it was hard to see “the devastation and heartbreak” experienced by NSW farmers.

“Apart from the comments being very insensitive to the plight of those farmers … it’s pretty dopey,” he said.