Treasury is being accused of not taking concerns over the pre-registration process for Mighty River Power shares seriously.
Greens co-leaders Russel Norman and Metiria Turei and Labour leader David Shearer have all been pre-registered for the shares.
Dr Norman complained to officials and was told it was likely a joke.
But he is furious and says someone fraudently using his identity is no joking matter.
"They said it had been done in jest, but how Treasury know the intent of the person who did this, I don't know.
"Whether it was done maliciously with intent to embarrass us, I don't know, but Treasury seems to know the intent of the person who did this, which surprised me."
The Minister of Finance has questioned whether the registration was actually just a stunt by opposition parties.