"They're not putting it in the back of teddy bears any more - they have reacted to how we react and that's the game that goes on.
"Every time we do something we're causing them to change their behaviour."
Customs officers had found drugs concealed in every imaginable way - stuffed into the bellies of fish, whole lounge suites made almost entirely of pseudoephedrine, drugs moulded into shoes and internal concealment.
"They're absolutely ingenious, anything that's got a cavity in it - chairs, tables. We've got plates that have got a very thin resin layer around it and virtually all contact NT (pseudoephedrine) inside."
Mr Day said there was a disturbing trend in substances intended to be sold as mimics of popular drugs such as Ecstasy.
"We have a situation where the chemical components are being changed and the purchaser of these drugs doesn't know what they are getting," he said.
"More and more people are presenting at [emergency departments] on a Friday night or a Saturday morning in a very bad way and doctors have been saying that it's because of a chemical cocktail that they've been taking."
Also of concern was the increased interceptions of "bath salts", so called because of their crystalline form, which have been linked to bizarre and violent crimes overseas.
"We don't want to sensationalise this but sooner or later these drugs are going to find themselves in the hands of some people and there will be one act that happens which will change our view overnight," Mr Day said.
The sale of drugs over the internet was also changing the face of the drugs trade and involving people who wouldn't usually be part of the criminal underworld.
"That presents a real problem for us at the border because we're getting new people into the market."
