"This is just appalling," Mr Dalton said. "We try so hard to make the city look great for both locals and visitors and you get something like this happening - it is absolutely mindless."
Mr Dalton said the repair job would be fast-tracked, however - "we don't give in to these sort of louts".
He dismissed any suggestions homeless people who sometimes slept under the platform may have been responsible.
"No way - it would not be them because they are not the sort of people who would do something like this," he said.
"This is the work of mindless vandals."
The glass barrier had allowed visitors to the platform an uninterrupted view out to sea and it had proved increasingly popular, despite earlier criticism that it did not extend out to sea far enough.
"This is the first time I've come to see it," a local woman walking a youngster said just after 8am yesterday. "They're just idiots - it's really disappointing."
A couple from Montreal who are visiting New Zealand as part of a cruise aboard the liner Noordam were also disappointed.
"It looks like a great spot to take photos from," one said.
"So sad when things like this happen - so sad."
The timing was bad in terms of the cruise ship arrival because the platform had been a popular spot for passengers who strolled the seafront.
The barrier was, however, shifted further out on to the platform and set up about 5m from the end so people could still walk most of it.
The glass wall was made of highly strengthened glass which Mr Dalton said would have required a lot of force to break.
It appeared the culprits had stood on the seaward side and used rocks from the shoreline.
As one maintenance staffer said - "you throw enough rocks at it and it'll break in the end".
Rocks could be seen strewn across the end of the platform.
Mr Dalton said the glass wall was an integral part of the design so that people could have an unobstructed view out to sea.
He said placing bars across the end would protect the glass but it was not an option council wanted to take. The cost of the damage was still being assessed.
Anyone who may have seen or heard any suspicious activity in the area overnight Wednesday and Thursday is asked to contact Napier police.