UNIONS do not believe the NSW Government's assurance that Hunter jobs will be protected in privatisation of the state's electricity.

Five busloads of Hunter union members attended the ALP state conference at the weekend to protest against privatisation.

"We've seen those promises before and they've never eventuated," Australian Manufacturing Workers Union state organiser Daniel Wallace said.

The Government could not guarantee jobs, Construction, Forestry, Mining and Energy Union energy division president Allen Drew said.

"Private companies will find ways and means of getting rid of people, like putting them in mundane jobs," Mr Drew said.

"The oldest guys will be worst affected."

Mr Drew said private owners of power stations would pay less attention to pollution control than state-owned generators.

The Government said private bidders must commit to "maintain local and regional employment".

The level of protection and certainty offered to employees would be a prime criteria.