The father of 6-year-old twins who broke their wrists when a blow-up slide blew away in strong winds hopes lessons have been learned from the incident which left four children hurt.

Kerikeri company Trailblazers Northland yesterday pleaded guilty to breaching health and safety legislation after four children were injured when the slide blew 20 metres off its site at a Christmas party.

The maximum wind gust recorded that day was 59km/h, about the time the slide blew away.

The Ministry of Business Innovation and Employment had charged Trailblazers Northland in connection with an incident at Whangarei's Heritage Park on November 17, 2012 under Section 16 (2) (b) (i) of the Health and Safety in Employment Act 1992.

Yesterday, the company pleaded guilty to a charge of failing to take all practicable steps to avoid harm at a workplace. The company will be sentenced on September 27, with the maximum penalty for the offence a fine of up to $250,000.

The slide had been secured to the ground by "pigtail" electric fence standards, stuck up to 15cm into the ground.

Heavy steel pegs that could be put 40cm into the ground were on site, but not used to secure the slide, while ropes or straps could have been used to secure the heavy steel pegs to the slide.

Trailblazers said this was standard practice, but could not explain why this had not been done on this occasion.

Anthony Hanlon's 6-year-old twin boys Kyle and Ethan were both injured when they were flung off the slide, with Ethan having both wrists fractured and Kyle his right wrist broken.

Mr Hanlon said it was frustrating that the company had the correct equipment on hand to properly secure the slide, but for whatever reason failed to do so.

He hoped that lessons had been learned by Trailblazers and any other companies that operated equipment around children.

"When it comes to kids, it's just not worth the risk [of taking short cuts]. The potential damage is not worth it and you may also end up getting prosecuted," he said.

Mr Hanlon said Kyle and Ethan weren't left with any long-term damage from the incident, but were reluctant to get on inflatable slides.

"We've been to a few parties since where they've had slides or bouncy castles and the boys always go and have a close look to make sure it's secured properly, which is quite safety conscious for a pair of seven-year-olds," he said.

ASB Bank staff from throughout Northland had gathered at the park for the bank's annual children's Christmas party when the incident happened last November.

The summary of facts said about 9.30am on November 17 one of Trailblazers' directors, Neil Sutherland, and two staff arrived at Heritage park with mini hot dog rides, an inflatable big slide and inflatable bouncy castle to set up.

About 11.45am a wind gust tipped and moved the slide about 20m onto the barrier of the mini hot dog rides.

A young girl suffered concussion after being flung off with the Hanlon twins, while a fourth child who was standing nearby suffered a small cut to his head.

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