A major exercise is under way to test New Zealand's preparation for a mass arrival of asylum seekers.
Immigration Minister Nathan Guy says the exercise will take place over eight weeks and begins with notification that a vessel is on its way.
The New Zealand Customs Service and Immigration New Zealand will process and accommodate the supposed asylum seekers after a simulated mass arrival at Devonport Naval Base in June.
Mr Guy says all agencies need to be prepared and the simulation will help test their planning.
He says a freighter with 500 asylum seekers was intercepted off the coast of Canada two years ago and if they can get there, he says, they can certainly get to New Zealand.
The Government is to introduce legislation aimed at deterring people-smuggling under which anyone arriving in a group of 12 or more could be detained under a group warrant.