Hundreds of fresh job losses were announced today when power firm E.ON told staff it was axing 450 posts.
Unison said the jobs will go from the company's retail, energy and business services departments and will be spread across the UK.
Dave Prentis, Unison's general secretary, said the job cuts showed that no sector of the economy was immune from the recession.
"While customers struggle with high water and energy bills, utility companies are making staff redundant.
"The competitive market system is fatally flawed, benefiting neither customers nor employees."
Unison said the Government and the regulator Ofgem should urgently review the operation of the energy market.
Donna Merriman, the union's officer for staff at E.ON said: "Unison is working closely with E.ON to make sure all those facing redundancy are given the support they need to find another job.
"We will be working hard to keep the human costs of these redundancies to a minimum."
Unison said that, as part of the cuts, a call centre in Glasgow will close and 54 jobs will be lost in Nottingham.Reuse content