GRAPHIC WARNING

The last words Jason Alexander said to both of his teenage daughters were "love you and be good tonight".

But they weren't enough to save his eldest, Tayla.

And her younger sister Sunmara is in a coma fighting for her life at Auckland's Middlemore Hospital.

On November 27, their father left the family's Ashburton home and left to see his partner.

Tayla Alexander. Photo / Supplied

Alexander has raised his two daughters on his own since their mother moved to Australia 11 years ago.

The girls then sneaked out of the house, got into an older teenage boy's car and headed toward Christchurch.

Tayla, 17, died when the car went over a bank and burst into flames on Summit Rd, on the Port Hills, about 11pm.

Sunmara, 15, was critically injured and has severe burns all over her body. Her father was told by doctors to "prepare for the worst".

"They told us Sunmara has 10 per cent chance of waking up from the coma," Alexander told the Herald on Sunday from the hotel he is staying in to be close to his only surviving child.

"And even if she does, there is a good chance she won't remember me or know who I am. That kills me.

"She has had four operations and two brain bleeds. She has massive burns all over her body. Her pelvis was smashed and she has a dead hand from the burns. They had to cut the rest of her skin off her and what flesh was left has been replaced with artificial skin. The biggest risk is infection - there is no skin to protect her," he said.

Last night Sunmara was breathing on her own. She has had four fingers removed from her left hand. Her right hand has just a thumb and one finger left.

Jason Alexander has opened up on the pain of losing one daughter, while a second clings to life in hospital, after a horror car crash. Photo / Sylvie Whinray

The driver of the car, whom Alexander doesn't want to name, has not been in touch or apologised.

"I have forgiven him. That's what Tayla would have wanted because that's who she was. It's just the right thing to do – we all make mistakes as teenagers. I can only imagine how scared and confused he must be feeling."

A police spokeswoman said no charges had been laid and the crash "remains under investigation".

But Alexander doesn't want the driver to be punished.

"I don't want them to go to jail for a silly mistake, they are young, so no. He is already going to have to deal with this for the rest of his life."

But he has a simple message to teenage drivers this Christmas: "Don't speed, there is no point. Speed was the main cause of the accident. It was just boys showing off to two pretty girls - it can happen so quick.

Sunmara Alexander. Photo / Supplied

"Twelve days ago everything was fine. Our lives got completely ripped upside down. Tayla wouldn't want me to break and Sunmara doesn't need me to break down either."

He wants to thank the teenagers who were the first to help at the crash site and acknowledges the courage of the firefighters who ran towards the burning car.

"They are the heroes."

Alexander has returned to Auckland after saying goodbye to Tayla at her funeral in Ashburton on Thursday. But he hasn't had any time to grieve.

He has left his home, jobs and pets to be with Sunmara but is realistic about the possibility he could lose her too.

Jason Alexander, with partner Lisa Campbell, forgives the driver of the car which crashed killing one of his daughter's and critically injuring another. New Zealand Herald photograph / Sylvie Whinray

"It's really tough, it's horrible, I can't sleep - they were my life. Sunmara is still fighting so I will keep fighting. I will stay here until I bring her home."

A Givealittle page has been sent up for Alexander.

He said the sisters were extremely close but had different personalities.

Tayla, who was studying art, was a "kind and gentle soul", who put others before herself, Jason said. "She wanted to be a psychologist to help people. She was very strong, caring and loving."

Sisters Tayla (left) and Sunmara Alexander. Photo / Supplied

Her younger sister, still at Ashburton College, is a "ratbag in a good way".

"She is fun-loving and full of energy. She would wag school and get caught because she would call Pizza Hut and get it delivered to the domain across the road from school. Her goal was to make lots of money. She had just started working at Countdown," Jason said.