He said the boat had come from the "safe" nation of India, and had not stopped anywhere else on the way.
"They haven't come from Sri Lanka, they haven't come from any of those other countries -- Afghanistan or anything like that," he said.
"They have come from India and as a result where they are safe in India, a passage to Australia here is nothing more than an economic migration seeking to illegally enter Australia."
The group, thought to be mostly ethnic Tamils from Sri Lanka and including women and children, left the Indian port of Pondicherry last month -- but their boat was intercepted by Australian authorities.
The asylum-seekers were then held in limbo on the customs ship until Morrison announced Friday they would be brought to Australia, where Indian consular officials would assess them with a view to taking them back to that country.
The group, now being held at the Curtin Detention Centre in Western Australia, is the first batch of asylum-seekers to reach the Australian mainland since December.
Morrison said Indian consular officials would travel to Curtin to determine their identity and residency, after New Delhi agreed to take back its citizens and consider taking Sri Lankans who were residents.
Those that refuse to return face being sent to camps in Nauru and Papua New Guinea in the Pacific for processing and resettlement under Australia's hardline immigration policies.
Morrison rejected the idea that they were fleeing persecution.
"I'd be surprised if anyone was seriously suggesting that people were being persecuted in India by the Indian government," he said. "If we can't take people back to India, what is next? New Zealand?
"So the suggestion that people have left a safe country are somehow fleeing persecution in India I think is absurd."
Morrison said India had asked for nothing in return for its cooperation on asylum-seekers.He also said Indian officials had been prepared to carry out the assessments at sea, but Australia had decided against this as it could take too long.