People's Vote campaigner Alastair Campbell has accused the group's chairman, Roland Rudd, of "sabotage", after he reportedly fired two senior staff members.
Campaign director James McGrory and head of communications Tom Baldwin were told to leave with immediate effect on Sunday night.
In an email, Mr Rudd - the brother of former Tory cabinet minister Amber Rudd - cited "internal issues in the campaign" as a reason to remove the pair.
"In difficult circumstances they have done a tremendous job. But as you will all understand the ongoing internal issues in the campaign have been allowed to carry on for too long. We now need a much clearer structure as we move forward," it read.
The sackings have left staff "incandescent", and they staged a walk out of a morning meeting today after they were told Mr Rudd would not address them.
A source told talkRADIO: "He [Mr Rudd] failed to turn up at a meeting he had promised and where staff had many questions for him. Instead, he decided to go on to Sky TV.
"Staff have now left the building with the exception of Patrick Heneghan [PV's acting chief executive] and some field staff who had been asked not to attend the meeting."
Mr Rudd has denied firing Mr Baldwin, claiming he has "an opportunity for a different type of role".
Mr Campbell shared his thoughts on Twitter
And Mr Baldwin insists that although Mr Rudd "technically controls my contract... he didn't appoint me. He doesn't pay me."
People's Vote member and former spin doctor to Tony Blair, Mr Campbell, said he was "very confused" by the events, and called the sackings a "deliberate act of sabotage and destabilisation".
He tweeted: "Very confused. @RolandRudd just went on radio and said there is no problem in @peoplesvote_uk campaign and nobody is being fired. Those letters sent to staff last night saying the campaign director and comms director have been fired must be forgeries then.
"Likewise the instruction to security not to let them in building today must have been imagined. He rightly said we are in touching distance of getting a confirmatory referendum. Hence the madness of a deliberate act of sabotage and destabilisation at this time of all times."
talkRADIO has approached the People's Vote campaign for comment.