Mike Tindall is to appeal against a £25,000 fine from the Rugby Football Union (RFU) for his controversial night out at the World Cup.
The Rugby Players' Association (RPA) described the punishment as "extraordinary" and "unprecedented".
Tindall has also been removed from England's elite player squad (EPS) for his behaviour in New Zealand.
Chris Ashton and James Haskell received suspended fines for a separate incident, with Dylan Hartley cleared.
Ashton and Haskell - both given suspended £5,000 fines and warned as to their future conduct after making inappropriate comments to a female hotel worker - are free to continue their England careers.
However, Tindall, at the age of 33, now appears unlikely to add to his 75 caps.
RFU operations director Rob Andrew said: "These actions have not been taken lightly but we believe that, in all these cases, the sanctions are commensurate with the level of seriousness of what occurred.
"While we acknowledge [Tindall's] previous good character, it needs to be made clear that what he did will not be tolerated."
Tindall wrote on Twitter that he wished to "thank" all his followers "for the support" over the RFU's ruling, while former England international Austin Healey wrote on his Twitter page that the £25,000 fine was "wrong" and claimed the player had been made a "scapegoat".
Healey, who earned 51 caps for his country, conceded Tindall had set a "bad example" but felt Andrew was "trying to justify his position".
The RPA, announcing the appeal, said: "The Rugby Players' Association has today noted the extraordinary fine handed down to Mike Tindall following the disciplinary process after the Rugby World Cup.
"Mike will be appealing this unprecedented fine as per the terms of the EPS agreement. There will be no further comment from Mike Tindall or the RPA at this time."
Tindall, married to the Queen's eldest granddaughter Zara Phillips, was defended by manager Martin Johnson following the night out, but the player later had to admit to misleading team management about events that evening.
During a troubled campaign that ended with a quarter-final defeat by France, there were also claims that winger Ashton, hooker Hartley and back-row forward Haskell had made offensive comments to hotel worker Annabel Newton.
"Regarding the events in Dunedin, it should be stressed that the allegations of very serious wrong-doing made against Chris Ashton, Dylan Hartley and James Haskell by Annabel Newton, a member of staff at the team hotel, were entirely false," said Andrew.
"We do not believe the players had any intention to sexually harass or intimidate Ms Newton. However, the incident is precisely the kind of dangerous, compromising situation the players were warned about prior to departure for New Zealand and that they were specifically told to avoid in the EPS code of conduct.
"While we found that Dylan Hartley played no part in the ill-considered exchange with Annabel Newton, Chris Ashton and James Haskell's behaviour did breach the EPS code of conduct.
"These episodes and the subsequent disciplinary action should stand as a strong reminder that the highest standards of personal conduct are expected from any England player, on and off the field."