A French tourist was dragged from his car and beaten, kicked and robbed by a gang of drunken youths in Christchurch's Hagley Park, Christchurch District Court was told today.

Judge Jane Farish referred to the damage the incident would have done to the city's reputation today when she sentenced unemployed man 24-year-old Joseph Henry Arthur Norris Mahara to four years and three months' jail for that and another drunken street robbery committed the same night.

"It's had a huge impact on the views of people coming to Christchurch - that it's not a safe place, and drunken persons like yourself can set upon people," Judge Farish said.

Mahara received a first-strike warning for the robberies, which were committed only about an hour apart last June 13, to which he pleaded guilty.

Five young people were in Victoria Square, in the central city, about 9pm when they confronted an 18-year-old walking home from work and demanded money.

When he declined to hand over his cash, the five allegedly pushed him to the ground, kicked him and took his bag containing his wallet and bank cards. They also took his reading glasses and cell phone.

The total value was $360 and although the victim was not injured, he no longer felt safe in the city.

Judge Farish said the group had been drinking and decided they needed more money to buy alcohol.

An hour later, the group was in the carpark of the Christchurch Horticultural Centre in Hagley Park when they found a French backpacker sitting in his car watching a movie on his laptop computer. He was a backpacker who planned to sleep in his car in the secluded area.

Mahara smashed the car window with a tyre lever, hitting the victim in the right cheekbone and showering him with broken glass.

He then reached inside and opened all the doors. The victim was dragged out of the car and repeatedly kicked and punched while on the ground while members of the group searched the car for valuables.

The victim appealed to the group not to take the laptop because it belonged to his sister, but the group only threw him on the ground again and gave him another kicking.

They took his car keys, computer and accessories, cell phone and a wallet containing his passport and credit cards. The total value was $2220 and none has been recovered.

The group ran off without taking his car.

The victim received a bloody nose and bruising to his face and body.

Two of the offenders, aged 14 and 15 at the time, were dealt with in the Youth Court, and a 21-year-old was jailed for three years and eight months for robbery and receiving stolen property.

An alleged fifth offender has pleaded not guilty and is due for trial late next month.

Defence counsel Allister Davis said Mahara expressed remorse in a letter to the judge, and Mr Davis voiced his apology to the victims on his behalf.

The pre-sentence report showed there was some hope for him but he was not prepared to undergo an alcohol rehabilitation course, despite being seen as a binge drinker.

Crown prosecutor Claire Boshier said the letter should be viewed with scepticism because of the limited remorse and acceptance of responsibility expressed in the pre-sentence report interview.

Judge Farish also viewed it sceptically but allowed a limited reduction of the jail sentence for remorse. She noted the triggers for his offending were seen as alcohol and a propensity for violence.

She gave Mahara a first strike warning and told him: "If you continue down this track you are never going to be able to be a father to your children.

"The only time you will see them is when they come to visit you in prison. You will spend all of your early adulthood in jail. That's the reality of the situation you are in."