It is thought the drugs found this year could have been used to make between 88kg and 124kg of methamphetamine and cause harm to the country estimated at up to nearly $50 million.
Since 2006, a total of 19.5 million tablets - enough to make more than 1.2 tonnes of P - have been intercepted in 3743 separate incidents.
The street value of P is about $1 million a kilo.
Customs officials said they could not comment on the reason for the drop in the number of seizures.
"Customs works with a number of agencies on combating the illicit drug trade, but we can only comment with authority on the number and nature of drug interceptions at the border," a spokeswoman said.
"Individuals attempting to import illicit drugs can go to great lengths to conceal them," she said.
"Passenger and postal screening allows Customs to manage passenger and package risk, and prevent these illicit drugs getting across our border."
A Massey University study released in September showed methamphetamine use in New Zealand may be declining following the National Government's action plan to disrupt supply of the drug.
The plan included banning over-the-counter sales of pseudoephedrine.
Prime Minister John Key said in the TVNZ leaders' debate last week that the higher seizure rate of pseudoephedrine and ephedrine was proof that the plan was working.
Last year's Illicit Drug Monitoring System report found that the price per gram of methamphetamine had risen steadily, and the drug's availability and potency had decreased.
"We were aware that the Government had put in place its methamphetamine action plan over the course of 2010 and we were interested to see what impact that had," said Dr Chris Wilkins from Massey University's centre for social and health outcomes research and evaluation.
"There seems to be a case to say that the Government plan has been making an impact.
"Certainly that increase in the gram price is really unusual when you look at international experience."
Ephedrine and pseudoephedrine are Class B2 controlled drugs. The maximum jail term for possession of a Class B drug is three months' imprisonment and/or a $500 fine.
The maximum jail term for supply or manufacture of a Class B drug is 14 years' imprisonment.
NUMBERS
2011:
1,963,121 pseudoephedrine and ephedrine tablets seized by customs officers in 465 incidents
438kg weight of the tablets seized
88-124kg possible P yield
$49.9 million financial cost of possible harm to the community
Since 2006:
19,511,991 tablets have been intercepted by Customs in 3743 separate incidents. They weighed 4350kg and could have caused harm to the community put at $384.5 million.
SEIZURES THIS YEAR
* Auckland customs officers intercepted packages from the United Kingdom and Thailand containing individually sealed and wrapped packets of the class C drug ephedrine with a total weight of 8kg. The packages had been declared as "herbal scrub powder" and could have produced between 3.5kg and 4.9kg of P.
* Christchurch customs officers caught a man returning from Thailand with 217gm of pseudoephedrine in his shoes and bag.
* After a joint operation between customs and police, Tauranga man Gary Read was charged with importing ephedrine, conspiracy to import the drug, possession of ephedrine for supply, and possession of methamphetamine for supply.
* Police allege that a parcel containing 1.8kg of ephedrine was sent from Thailand to a Tauranga address and Read's daughter delivered the parcel to her father within an hour.
