TVNZ and the Government have been accused of keeping the increasing popularity and awareness of TVNZ7 under wraps before the public service channel's axing.
The survey, carried out in May last year, has now been made available, but was not enough to stop TVNZ7 being scrapped in July and replaced with a delayed feed of TV One.
It showed 91 percent of people who had heard of TVNZ7 believed it was important to New Zealand and awareness of the channel grew from 32 percent in September 2008 to 74 percent in May 2011. It was being watched weekly by more than half of all Freeview households, even before the digital switchover.
Lobby group Save TVNZ7 successfully sought the report through the Official Information Act.
If the survey had been made public it may have influenced the entire debate about the channel's closure, spokesman Myles Thomas told NZ Newswire.
"It makes you wonder whether there was any other motive to keep it from the public view."
But TVNZ spokeswoman Megan Richard says the survey was not released as it contained information the company considered commercially sensitive, despite TVNZ7 being non-commercial.
The report went to then broadcasting minister Jonathan Coleman and was later included in TVNZ's annual report.
TVNZ was under no obligation to release the survey at the time as it could not lobby or appear to lobby the Government, she said.
Dr Coleman announced TVNZ7's closure in 2011, saying it only had a weekly audience of 207,000.
However, he later admitted the figure, which he said was provided by officials, had been calculated wrongly.
Labour broadcasting spokeswoman Clare Curran said the debate around the closure would have been very different if the report had been available.
Around 700,000 people were watching the channel each week, she said.
"If New Zealanders had been aware and if the government had owned up to the extent of TVNZ7's audience it would have been a lot harder to justify canning its funding."