The Minister for Primary Industries (MPI) will be asked to explain why he continues to allow palm kernel expeller into the country when numerous biosecurity flaws have been identified in its supply chain.
Nathan Guy will appear at the Primary Production Select Committee on Thursday morning at Parliament - the day after his ministry changed its tune on the origin of an animal limb discovered in May on a Bay of Plenty farm in a palm kernel delivery.
MPI says DNA testing has revealed the leg came from a sheep - and not from a goat or deer as it announced last week.
The ministry believes it was a New Zealand sheep partly due to the origin of maggots found on it.
Yet farmers who've seen the limb say it was too small to have come from a New Zealand sheep - and point out it was found on a dairy farm.
Labour Party agriculture spokesperson Damien O'Connor said the select committee wants answers on why palm kernel is still being allowed in.
He said conservationists, grain farmers and other farmers realise this is a serious risk.
But Mr O'Connor said farmers who are dependent on palm kernel, particularly during periods of drought, are reluctant to admit that maybe they should not be using it.
He said there are a lot of vested interests that make change difficult.
"But it is up to the minister, it's his job, to give an absolute assurance that biosecurity as he says is the number one priority and he follows it through with some actions".
A recent report by MPI officials found palm kernel could be coming from unapproved plants in Malaysia and Indonesia, and that rodent and bird control measures at some plants were substandard.