The Prime Minister was warned that fewer seizures of the drugs used to make methamphetamine were a sign smugglers had changed their methods - rather than less drugs coming into the country as previously stated by a Cabinet colleague.
The warning came shortly before a record haul of pseudoephedrine was discovered in Auckland.
Operation Ghost found 330kg hidden in three safe houses and detectives believe another 142kg was imported in May. Intercepted conversations led to another 248kg being stopped at the port.
Seizures of pseudoephedrine, which is a legal cold medicine in China, had been steadily falling over the past four years since government measures to curb the P trade.
The Customs Minister, Maurice Williamson, said 300kg of precursor drugs had been found in 2012 - down from a record 1.2 tonnes in 2009.