Transport Minister Andrew Constance signed off on the plan and later went ahead with naming the vessel Ferry McFerryface, the Nine Network says.
The documents reveal environmental campaigner Ian Kiernan received the most votes in the competition which cost $100,000.
Hours after the documents were released on Tuesday, Transport Minister Andrew Constance announced the vessel, which he says was branded as Ferry McFerryface for the summer only, will be renamed.
"We always intended this vessel would be named for the kids," Mr Constance said in a statement.
"After a summer on the harbour, Ferry McFerryface will now be renamed after prominent Australian author May Gibbs. This will retain the vessel's appeal to our youngest customers while also recognising an Australian icon with a long connection to Sydney."
NSW opposition spokeswoman Jodi McKay slammed Mr Constance saying he had been caught out "rigging the ballot".
"We know Andrew Constance can't run a train network but now it's clear he can't even run a competition to name a ferry," she said in a statement.
"He flat out lied about the competition repeatedly saying Ferry McFerryface was the popular choice when he knew it was anything but."
Earlier, Mr Constance denied the claims, saying the reports were "incorrect".
He said Ferry McFerryface came from the first open call for public nominations where people could vote for any name without stringent criteria.
"In this round, Ferry McFerryface received 229 nominations and Ian Kiernan received 17," Mr Constance told AAP in a statement.
The second round of public voting included set criteria and did not include Ferry McFerryface as an option, he said.
The name Ferry McFerryface is not original. It follows a public vote in the UK to name a new polar research ship Boaty McBoatface but the Natural Environment Research Council choose "Sir David Attenborough" instead.