Lance Teriwhi Corkery will spend less than five years in jail for inflicting injuries on a baby that left her in a condition like that of a stroke survivor.

The 39-year-old unemployed Whangarei man "lost it" when his girlfriend's child, Tinishar Walker, 17 months, was crying. He picked her up, shook her violently and dropped her twice so her head slammed against an open drawer as she fell to the floor.

Tinishar, now 22 months, is still recovering from the "cowardly attack" and is barely able to walk by herself, struggles to feed herself and has to wear a protective padded helmet in case she falls.

She wears a splint on her left leg for support as that side of her body is the worst-affected. She will need help for the rest of her life. Medical experts say her condition is similar to that of someone who has had a stroke.

Yesterday Corkery appeared in the Whangarei District Court for sentencing after he admitted causing grievous bodily harm to Tinishar with intent.

Judge John MacDonald sentenced Corkery to four years and 10 months in jail, with a non-parole period of two years and five months.

Tinishar's family is struggling to see how such a "short sentence" was dished out for injuries that will affect her for ever.

Grandmother Tina Nicholson said there was no way the prison term compared to the permanent damage done to her moko.

"My beautiful moko will never have a normal life. He beat a baby in a cowardly attack," Mrs Nicholson said. "This just sends out a message to those who do this sort of thing they will just get a slap on the hand."

For Ms Nicholson, sitting in court during sentencing, it was the first time she had heard of the attack details. "It was gut-wrenching to listen to it in court and think someone could do that to a child."

Tinishar's 19-year-old mother, Siobhean Cassidy, said the punishment was "unfair".

"It breaks my heart to see her. Sometimes she just gets frustrated and she should be running around and enjoying herself. She will have to have help for the rest of her life."

Crown prosecutor Mike Smith said it was a miracle Tinishar had survived the prolonged attack and recommended nine years' jail.

Defence lawyer Arthur Fairley offered an apology from Corkery.

He said Corkery had pleaded guilty as soon as he could, was extremely remorseful and had suffered a brain injury himself five weeks before the attack.

Judge MacDonald said Corkery had been in a defacto relationship with Miss Cassidy at the Windsor Ave, Kamo, house. Last August 11, Corkery was at home looking after Tinishar. His mother was watching television in another room.

Corkery put Tinishar down to sleep but picked her up when she started to cry and violently shook her. Her head flung back and forth, causing a brain bleed.

"You would have had to have lived in a box of cotton wool over the last five years not to have known that this is what happens when you shake a baby," Judge MacDonald said.

Corkery then held Tinishar out in front of him and dropped her from waist height. The back of her head struck an open drawer. Corkery dropped her again, then carried her to the shower to clean her up, but she fell over.

Corkery rang Ms Cassidy, saying Tinishar had injured herself in the shower and asked what he should he do. A short time later he called an ambulance.

Tinishar was lapsing in and out of consciousness and when she arrived at Whangarei Hospital, she was given urgent life support.

A scan showed a fractured skull and a brain bleed. She was flown to Starship in Auckland where she went straight to theatre to have part of her brain removed to relieve the pressure.

More brain bleeds had doctors fearing for her survival.

When spoken to by police, Corkery said he had lost it when the baby would not settle.

Judge MacDonald said the starting point was eight years and he was bound by law to give a 30 per cent reduction for an early guilty plea. He also gave a six-month reduction for Corkery's brain injury.

Tinishar remains in an Auckland rehabilitation centre and requires one-on-one daily help.