Former home secretary Alan Johnson - an ex-union leader - warned against "petty retribution" in the wake of Ed Miliband's party reform pledge.
"We can no longer go on living the lie with these millions of people signed up as levy-paying members to the Labour Party, and treated as if they were members," Mr Johnson told BBC Radio 4's The World At One.
"I call them the ghosts in the machine. That is bad for the party, it is bad for the trade unions."
The former Communication Workers Union chief added, "I just hope this is not a piece of petty retribution by a trade union."
Former Home Secretary Alan Johnson has said he is in complete agreement with Theresa May on the need to pass the Communications Data Bill before the general election.
He told the BBC's Andrew Marr Show: "We need to get this on the statute book before the next general election and I think it is absolutely crucial.
"Indeed I think it is a resignation issue for a Home Secretary if the Cabinet do not support her in this central part of what the security services do."
The Communications Data Bill - dubbed the "snooper's charter" by its opponents - would give security forces greater powers to monitor communications such as emails.