"The act of cooking over an ancestor is tapu - it's something that you just don't do," Taranaki DOC boss Phil Mohi told the Taranaki Daily News, which posted video footage of the group's efforts on its website.
The barbecue was particularly disappointing because the young people there did not realise or had not learnt the mountain, and especially the summit, was a very sacred place for Taranaki iwi, he said.
"We discourage camping at the summit and try to make people aware that the very highest part is the most sacred of all - and ask climbers to avoid standing there. There's a difference too between eating prepared food for sustenance and actually cooking on the summit," he said.
Barbecue organiser Jordan Millen said he was unaware the group's actions were offensive.
"We are sincerely sorry for any offence we may have caused during this trip on Mt Taranaki, we were unaware of any tapu or the sacred nature of the summit and that it was not respectful to cook there," he said.
Mr Mohi was also offended by old graffiti on the summit rock, which he felt showed people went out of their way to cause offence.
