On Wednesday Dujardin had her UK Sport funding suspended pending the outcome of the FEI investigation, while she has also been dropped as an ambassador for horse welfare charity Brooke.
Two of her sponsors, equestrian insurance company KBIS and Danish equestrian equipment company Equine LTS, have terminated their deals with her.
World Horse Welfare chief executive Roly Owers said the Dujardin case is a “massive wake-up call for anyone who thinks this is not important”.
He added: “This story is another salutary reminder of how vital it is that equestrians put the welfare of the horse first, all of the time, whether in the competition arena or behind closed doors.
“Respect for the horse must be at the heart of every equestrian, and every equestrian sport, and their actions must demonstrate that respect all of the time.
“World Horse Welfare actively supports horse sport, but there cannot be any tolerance for unacceptable practices, no matter how experienced the rider or coach.”
Claire Bass, the UK’s senior campaigns director for Humane Society International, told BBC Radio 5 Live: “It is not a case of one bad apple or necessarily Charlotte’s behaviour being egregious. With the whole industry the cart is rotten.
“Exposes like this lifts the lid behind the curtain on the cruelty that is inherent in these types of sports.
“If people want to get a medal for dancing then they should take part in the new breakdancing event at the Olympics.”
However, top dressage instructor Pammy Hutton told BBC Sport she hoped it was “out-of-character” for Dujardin, having never seen her use a whip in that way before.