"The board undertook three months of public consultation on these proposals from April-July this year, with the overwhelming majority of public submitters showing that they wanted the choice to use the English or Maori names.
The board received 2608 submissions from 1329 submitters.
Of the submissions, 1842 were in support of one or more of the proposals and 766 opposed to one or more.
"That said, the numbers were not the main consideration - the board is guided more by submitters' reasons for supporting or objecting, and our recommendations were informed by careful consideration of all submissions,'' Dr Grant said.
Following Mr Williamson's announcement, Land Information New Zealand maps and charts that feature the island names will reflect both the English and Maori names.
This will occur only as maps and charts come up for revision in the normal course of maintenance.
Mr Williamson said while the names appeared in official publications, including maps and charts, they had been recorded names only and had no formal standing.
Tourism New Zealand communications manager Deborah Gray said it was too early to say whether the decision would affect marketing and advertising material by including the alternate Maori names.
A KiwiRail spokeswoman said with the announcement only just being made, it was ``yet to form a view'' on whether to change their advertising material to reflect both names.
An Air New Zealand spokeswoman also said it was too soon to know if the changes would make a difference for the business.
Mr Williamson said people could use either the English or Maori names or together if preferred.
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What they're saying on Twitter:
* @nickford: "NZ's north and south islands will henceforth be known officially as North Island and South Island, at least in English.''
* @duckenvy: "Stewart Island will now be called Williams Island The South Island will hereby be called Bill, and The North Island is to be called Sonny.''
* @2TAPU: "And in Breaking News the Govt OFFICIALLY names the North Island & South Island (Oh & you can use those other Maori names if you want to ...)''
* @LI-politico: "Ka pai! Proper names for our two islands. :) They are Te Ika-a-Maui (North) and Te Waipounamu (South).''