The largest seizures of methamphetamine and cocaine imported into New Zealand kept the Customs Service busy in 2016 and 2017.

In mid-2016, 176kg of methamphetamine concealed in the doors of shipping containers was uncovered after a 16-month investigation, while late last year Customs was an integral part in 46kg of cocaine - worth an estimated $20 million – being seized in Tauranga.

According to Customs' 2016-17 report, drugs worth $329m were intercepted at the New Zealand border in those two years, which could have potentially caused $1.15 billion in social and economic costs to the country.

All up, 353kg of methamphetamine was seized – up from the 294kg taken by Customs in 2015/16 - along with 725kg of drugs or chemicals used to make the methamphetamine.

The countries methamphetamine is originating from is changing, too.

"In 2016–17 we have seen a change from China, Hong Kong, and Taiwan as the predominant source countries due to a rise in North American smuggling routes (Canada, the United States, and Mexico)," the report said.

Criminal syndicates bringing in ecstasy is also on the rise, along with smaller amounts coming in through the mail stream after being bought over the dark web.

"This resulted in us intercepting 32.3kg in crystal form and over 5000 tablets in 2016-17, compared to 6.6kg and nearly 6000 tablets in 2015–16."

The report also said 44,520 individual counterfeit goods items were seized.

In terms of travellers, 13.3 million people were processed arriving and departing New Zealand shores, a record for Customs and more than 9 per cent more than in 2015-16.

A record $13.3b in revenue was collected by Customs in 2016–17, in duty and taxes, making up about 18 per cent of the Crown's annual tax revenue.