A former Brook House officer and whistleblower has been questioned on failing to report abuses, before filming them for a BBC documentary.
A public inquiry is ongoing into the mistreatment of immigration detainees at the removal centre, near Gatwick.
Callum Tulley said there was "no alternative" to his 2017 Panorama report as complaints were "fruitless".
The inquiry also heard managers at the centre failed to discipline or search officers accused of drug smuggling.
During the inquiry it was put to Mr Tulley: "You could have reported [abuses] to the centre manager or the Home Office if you were concerned about what you were seeing."
He replied: "We know... that complaining through the channels that ostensibly existed that you were marginalised and pushed out."
When asked why he did not complain anonymously Mr Tulley said: "What evidence would I have had? Who's word would it have been? Mine against the officers who would have closed ranks and denied what happened.
"The abuse of detainees happened in cells, there were no cameras. I would have needed people to complain with me or it would have been fruitless."
He was also accused by another officer, Yan Paschali, of being biased.
It followed a choking incident in 2017 when Mr Paschali held a detainee down by his neck.
Mr Paschali accused Mr Tulley of cutting out parts of the footage in which he claims to have saved the detainee's life.
Mr Tulley denied this and said all the unedited footage is able to be viewed by the...
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