Unison is concerned that time is running out for making claims and it is urging members to come forward quickly if they want their complaints investigated.
National pensions officer Glyn Jenkins said: 'We have given this step considerable thought. We are dissatisfied with the progress being made by the life and pensions industry.
'We feel that we must move now to protect our members' position and we are asking any member who believes that they have been given misleading advice about the right pension for them to contact Unison.'
Mr Jenkins said: 'Many people were encouraged by this government to make their own pension arrangements. Unfortunately this has left may people vulnerable to high pressure selling from life companies and instead of looking forward to a secure and happy retirement they are facing the prospect of scrimping and saving just to make ends meet.'