It was feared the 42-year old father-of-eight, of Linwood in Christchurch, might die from his injuries, and he was in an induced coma for several weeks.
After the serious incident, a investigation launched by the former Department of Labour found several breaches of the Health and Safety in Employment Act at the site.
However, the breach admitted by Fletcher Construction Company Ltd does not relate to Mr Ngatai's accident, which has been the most high-profile incident since the massive demolition process of the quake-decimated city's CBD.
Judge Raoul Neave said today at Christchurch District Court that the only relevance of Mr Ngatai's fall to this case was that it provided the "trigger'' for the probe which found the health and safety breaches.
The judge said Fletcher had given "considerable assistance'' to Mr Ngatai since his accident, which reinforced views that it was a "highly responsible employer''.
But the breaches were serious and the consequences were "potentially disastrous'', the judge said.
Fletcher admitted failing to "take all practicable steps to ensure the safety of its employees while at work''.
The general manager of Fletcher Construction, plus senior management, including the health and safety manager, were in court today.
Fletcher lawyer Graeme Christie said the company accepted its responsibility and knew it needed to be held accountable.
The hotel, Christchurch's tallest building, was being taken down floor by floor in a process described as New Zealand's biggest ever demolition project.
While work was being done to remove columns and beams, a colleague saw Mr Ngatai, who had worked at Fletchers for six years, fall from a ladder between floors 23 and 24.
Health and safety inspectors found damaged ladders, while exposed work edges meant workers could have fallen to lower levels of the hotel.
It also found the floor area where the accident occurred had `penetrations' which had been covered "loosely'' with plywood and were not adequately secured or identified with signage.
The former Department of Labour, now part of the Ministry of Business, Innovation and Employment, made four recommendations for Fletchers to undertake to improve safety, which they have done.
It said workers should be protected by working at height from within an enclosed platform, and guardrails or bump rails should be placed around exposed perimeter edges.
The company should also cover floor penetrations and warn workers by erecting signs.
Ladders should also be "fit for purpose'' and "tied off or footed''.
Judge Neave said it was a case of a systems failure, rather than lack of systems.
He said it was the company's responsibility to be "constantly vigilant'', but accepted Fletcher had acted on the recommendations promptly.
The Labour group's lawyer Alex Leulu said the hazards identified were "real'' and an accident at the site was "inevitable''.
"Mr Ngatai's accident is an example of what happens when someone does fall from height,'' he said.
The Government says safe working at heights remain "a key focus'' and Mr Barton says everyone involved in the rebuild needs to "commit to rebuilding Canterbury safely so that this prosecution is `the last one' for Canterbury.''
