The Daily Telegraph have reported that Brook, Jacob Bethell and Josh Tongue could be subject to an investigation from the cricket regulator with regard to the incident in Wellington, which occurred the night before a one-day international which England lost.
The incident, which happened in November, did not come to light in the media until January, and followed a mid-Ashes break in Noosa which also drew criticism for some excessive drinking by players.
“Cricket is 12 months a year, you have to be able to enjoy yourselves. I don’t think the boys went overboard at all,” McCullum said of the Noosa trip.
“A lot of the pile-on for it was completely out of line. Noosa is where people go and retire, there’s a reason why we chose Noosa.
“It’s being made [out] as this big stag do place, it couldn’t be further from that. If we wanted a stag do and we wanted a tear up, we’d have gone to the Gold Coast.”
McCullum’s leadership style has drawn criticism from outsiders, with some feeling the players are given too much freedom on and off the pitch.
However, McCullum bristled at such sentiments and believes his message has been misinterpreted by those outside the dressing room.
“I think you guys [journalists] have got to work me out a little bit better to be honest,” he said.
“If you go back to the day I walked into the job, the first thing I said to these boys is don’t do anything that lands you on the front page of the paper and nothing good happens after midnight, but we’re going to have a good time.
“[I said] we’re going to grow, we’re going to enjoy ourselves, cricket is a tough game, it has its challenges mentally, which we’ve seen with many people that have played cricket in the past, but we’re going to try and play a style of cricket that allows us to succeed.
“I’m not against making sure these boys are controlled in a manner. It’s [about] looking after them to ensure they don’t make mistakes. The curfew is a different interpretation of the words I mentioned three and a half years ago.”
McCullum said he thought there was a “misconception” that he ran a “loose ship” and wanted everyone out drinking, and that he didn’t care about cricket.
“It couldn’t be further from the truth,” he said.
“I’m fiercely determined, I’m fiercely competitive and I want the best for these guys, and I want the best for English cricket.”
England start their World Cup campaign against Nepal on Sunday, 8 February (09:30 GMT).
Brook will lead the team in India and Sri Lanka and McCullum says he is impressed by the Yorkshireman’s captaincy so far.
“I think Harry Brook is an outstanding leader on the field,” he added. “His tactical acumen is as good as I’ve seen in a short period of time from a young man.
“He has work to do off the field without a doubt, as do some of the other young lads we have in our side – and that’s what happens when you come in at 20 and you’re growing up on a world stage with spotlight, fame, fortune and the pressure that comes with it.
“He’s a strong leader, he’s a young man but he’s got a very good head on his shoulders. People will say he’s not that clever, I couldn’t disagree with that more, he wears his intelligence lightly and he’s a very strong leader.
“He’s a player they play for in that dressing room and our job is to keep looking after him because he is young and he’s got his best days in front of him.”