Thousands of power workers and community members have demonstrated at Parliament House warning of the dangers of electricity privatisation.

The message was clear from protesters in the state capital, as well as in regional centres in NSW - electricity is too important to be put at the whims of big business.

A poll released today backed the people on the street, reporting that 64% of NSW residents were opposed to the plan.

AMWU NSW Secretary, Paul Bastian, said that unions and community opposition had won the battle against electricity privatisation once before, and could again.

In a sign that the tide is turning against Morris Iemma and Michael Costa, over a dozen Government backbenchers left parliament house to join the rally and show their opposition to the plan.

Graham Middlemass, a power worker from Victoria, where power was previously privatised, said that prices had increased in the southern state.

"Workers and their families will get higher prices, reduced service reliability and local jobs and services being sent offshore as a result of the sell-off," he said.