PRIME Minister John Howard last night defended spending huge amounts of money to ship asylum seekers to Christmas Island even though they have full access to Australia's courts.

Immigration Minister Philip Ruddock confirmed a rickety fishing boat carrying 53 Vietnamese asylum seekers entered Australia's migration zone when it sailed towards Port Hedland on Tuesday.

That means the 27 men, 17 women and nine children can appeal any refugee decision with the Refugee Review Tribunal (RRT) and access Australia's court system.

It also means the decision to ship the asylum seekers 1,800km from Port Hedland, which houses a large immigration detention centre, to Christmas Island was unnecessary for legal purposes.

But Mr Howard said it was the right decision.

"We have a very clear policy and that is that people who seek to come to the country illegally will not be allowed to come to the mainland," he said.

"If we didn't (send them to Christmas Island) we would send a message of encouragement for other people to try the same thing.

"It is perfectly justified and I'm sure will be supported by the Australian people."

Labor described as a monumental stuff-up the move to have the Navy frigate HMAS Canberra pick up the Vietnamese boat people from the West Australian coast and take them to Christmas Island, where the detention centre had been closed.

But Labor's new immigration spokeswoman Nicola Roxon fell short of demanding their return to Port Hedland. "We now know that the government rushed, that the minister made a bad judgment, that he didn't get advice and he is now putting the Australian people to great expense for no particular purpose," she said.

HMAS Canberra was expected to deliver the asylum seekers to Christmas Island this afternoon local time.

Opposition Leader Simon Crean described the situation as another example of government deceit.

"Yesterday the government said it wasn't in territorial waters," he said.

"They deceived on the kids overboard, they're still deceiving on their border protection policy."

It was originally thought the asylum seekers would be processed on Christmas Island.

The island was excised from the migration zone in 2001, meaning asylum seekers processed there have no right to use Australia's legal system.

But Mr Ruddock today revealed the boat reached Australian port waters, which qualifies all 53 aboard to access the courts.

Refugee umbrella group A Just Australia said processing the asylum seekers on Christmas Island would lead to long delays and promised to ensure they received legal access.

Meanwhile, a 46-year-old Australian citizen who was aboard the boat made a brief appearance in South Hedland Magistrates Court yesterday charged with smuggling the 53 Vietnamese to Australia.

Van Hoa Nguyen was arrested after the boat was intercepted and charged with illegally facilitating passage to Australia, which carries a maximum 20-year jail sentence.

Nguyen was remanded in custody and ordered to appear in Perth Magistrates Court on July 18.

AAP