Jen de Montalk says one of the masked men flashed his genitalia while another launched a vicious attack on her daughter's friend at about 5:30pm on Saturday evening.

"One of them exposed himself and one of them choked the boy after calling him a f****t," she said.

"My daughter got clipped by a stray punch and the strangler also head-butted the boy. They also stole the boy's phone but the kids got it back.

"After the assault, my daughter managed to persuade one of the train staff to kick them off. They got off at the Baldwin St station."

Ms De Montalk says despite the violence and obvious intoxication of the men dressed in Four Square costumes, fellow commuters and train staffers failed to offer help the teens.

"No one helped the kids fight them off, including two train staff who were there, but people were filming it," she said.

"This was a serious assault on a pair of 15-year-olds, fuelled by alcohol. Shame on Auckland Transport and shame on those who sat by and did nothing."

Ms De Montalk says police are now involved as she wants to "make sure we get these degenerates".

Police told Fairfax they had not been able to locate the men, but were continuing with inquiries.

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