Neck injuries were most common, followed by chest, head and lower back injuries.
Ministry of Transport manager Brent Johnston called the increase disappointing, saying the lingering effects of serious injuries could have a huge impact on people's ability to enjoy their lives.
Provisional Ministry of Transport statistics for last year show 12,200 people were injured, more than 2000 of them seriously.
This was an increase of 981 compared with 2014, the first time the number of people injured on the roads had increased in the past five years.
When adjusted for the amount of cars on the road, the number increased from 33 people injured per 10,000 cars in 2014 to 35 last year.
In 2011, 39 people per 10,000 were injured in car crashes, a number which had been steadily decreasing until last year.
The official road toll also increased by 26 to 319 deaths last year and Johnston said this year was not off to a good start.
"So far 118 people have been killed on the road, and 297 people seriously injured. This is quite simply a tragedy for the individuals involved, and their families and friends.
"Every death on the roads is a tragedy and injuries from road crashes can have a long-term effect on people's ability to be productive and enjoy their lives.
"There are simple things that people can do to keep themselves and others safe, such as wearing seatbelts or motorcycle helmets, driving sober, travelling at an appropriate speed within the speed limit."
As part of an ongoing mission to reduce the amount of crashes on our roads, the Government will release the third Safer Journeys Action Plan 2016-2020 shortly, Johnston said.
AA road safety spokesman Dylan Thomsen said the increase was a huge concern and not a problem with an obvious cause.
There had been a slight increase last year in the number of vehicle kilometres travelled throughout the country, "but not in line with the increase we've seen in crashes".
"There's still a lot of unknowns," he said.
"We're not sure why we have seen the crash rate start to increase again but what we're focused on is how to turn it around."
Road quality, vehicle safety and safety measures like median barriers and rumble strips were all practical measures the AA supported to get the number of crashes down, Thomsen said.
Repeat drink-drivers also played a part in crash statistics and the AA was waiting to find out whether its proposal for the mandatory installation of alcohol interlocks in the cars of repeat offenders would be approved by the Government.
An alcohol interlock acts like an in-car breathalyser. The driver must blow into the device before driving and if any breath alcohol is detected the car won't start.
Thomsen said about 2 per cent of recidivist drink-drivers in New Zealand had alcohol interlocks installed, but it should be mandatory.
"Overseas research has shown more than 50 per cent reduction in the rate of re-offending where alcohol interlocks have been introduced," he said.
"They're the best weapon there is out there for fighting drink-driving."
Meanwhile, Ministry of Transport data also reveals the most common time we crash on the roads.
Latest data shows crashes causing injury most commonly occur during peak weekday traffic hours, including between 8am and 9am, and 3pm and 6pm.
In 2014, the highest number of crashes causing injury in an hour (132) occurred between 4pm and 5pm on a Wednesday.
