A driver today admitted causing the death of a four-year-old boy who was walking on the pavement when he was hit by the teenager's car.

Ashley David Austin, an 18-year-old Christchurch shop assistant, pleaded guilty to driving in a manner that caused the death of Nayan Woods and the injury of Nayan's older brother Jacob, 6, and mother Emma in May.

Austin's car slid from side to side on the road before climbing the footpath and hitting the family, who were walking along Linwood Avenue in central Christchurch.

Jacob received multiple fractures in the collision, while Mrs Woods escaped with only minor injuries.

Austin also admitted a charge related to the modification to his vehicle while a second similar charge was withdrawn in the Christchurch District Court today.

Judge Noel Walsh remanded him on bail for sentence on October 20.

The judge called for a pre-sentence report, and emotional harm reports and victim impact reports on the injured family members.

Defence counsel Jonathan Eaton said a possible arrangement for a restorative justice meeting "continues to be addressed between the families".

Police prosecutor Sergeant Ayson Williams said Austin had been working as a shop assistant on May 21 when he left Eastgate Mall in Linwood, in a Nissan Sylvia car. He had not been drinking.

The car was registered to his mother but he had been the operator of it for the previous two months.

As he turned into Linwood Avenue he accelerated hard and his car made a loud noise. He did what was described by a witness as "a controlled drift". As he changed up into second gear, the rear of the car swung out and he lost control.

It crashed backwards across the footpath and into a fence, striking the three members of the Woods family. Emma Woods received bruising, Jacob received multiple injuries including broken bones, and Nayan received non-survivable injuries. He would have become unconscious immediately and death would have been rapid, said Mr Williams.

The Nissan had been modified and some of the changes did not comply with the traffic regulations. It had modified springs and the shock absorbers had been lowered. The lowered suspension allows the car to slide more easily but it was only suitable for restricted areas and not on public roads.

Mr Eaton said Austin's loss of control was caused by excessive acceleration and loss of control, and not by deliberate drifting.

- With NZPA