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Wildlife authorities have defended the way an orphaned whale calf was put down yesterday, following criticism that it suffered before dying.

The injured baby humpback, affectionately called Colin _ but which has now been identified as a female _ was put down by veterinarians after being abandoned in waters north of Sydney earlier this week.

Cherie Curchod said she saw the whale thrashing around near a jetty below her home after it was given more than six injections.

Ms Curchod said the whale was then tied up and dragged across the bay at Bonnie Doon, to The Basin at Pittwater before it "actively started trying to get away. Then they dragged it to a closed tent and all the while it was flapping its tail, blowing out of its head and trying to get away", she said.

National Parks and Wildlife spokesman John Dengate said the whale's death was the "best possible result" in the circumstances.