Radio spectrum used by wireless microphone users cannot be protected unless it is paid for, says Communications and Information Technology Minister Steven Joyce.
A lobby group of concerned users says the technology's use in gyms, theatre, sports and tourism is in doubt as work progresses to switch from analogue to digital television signals - a move that will reallocate the available spectrum.
Mr Joyce says some of the concerns raised by the group, such as interference between users, are already true.
He admits the band will narrow, but there will still be spectrum available - provided wireless users do not interfere with others who have invested in spectrum space.
Analogue television signals are scheduled to be switched off by 2015.
But a lobby group, Wireless Users New Zealand, says the existing general licence band for wireless microphones will be changed, leaving much less bandwidth.
Chairman Stephen Buckland says users are reluctant to replace or buy expensive equipment without assurances about which frequencies will be open.
Mr Buckland says officials underestimated the number and variety of wireless users.
He says there are serious doubts about whether there will be sufficient spectrum for professional users in Auckland and Wellington, and for coverage of large events.
