Trade union GMB attacked Prime Minister Theresa May over her statement in the Observer that she would "fine greedy bosses who betray their workers".
Michael Ainsley, GMB Regional Officer, said:"Fine words are not enough because right now water utilities and other former public sector employers are preparing to rob workers of tens of thousands of pounds out of their pension pots."
He said some utilities were at an advanced stage of ending final salary pensions for workers.
"Their excuse is pension deficits, which they have had plenty of opportunity to fund but have preferred to fund instead large salaries, bonuses and pensions for executives, and pay huge dividends to shareholders, which include pension funds themselves," he added.
The GMB union is writing to Work and Pensions Committee chair Frank Field over some utilities' pension funding and tax arrangements.
