The Government's being told to think carefully, before deciding whether or not to approve a carp farm near Lake Taupo.

A proposed grass and silver carp farm, which would sit in the Taupo industrial area, has already been approved by the Department of Conservation.

Federation of Freshwater Anglers executive member Alan Simmons said silver carp are an extremely invasive species that could put Taupo's clean image and trout fishery at risk.

He says it's mind-boggling the Minister of Conservation, who'll be deciding on the proposal in the next few weeks, could let it get this far.

"Maggie Barry's got to have rocks in her head to let anything like this near Lake Taupo.  The Conservation Minister should be protecting Lake Taupo."