The firm is calling on the Government to change the rules so that saving in a personal account does not affect enhanced protection, which protects people from a 55 per cent tax charge if they go over their lifetime allowance.
Savers who have registered for enhanced protection will see it invalidated by being auto-enrolled as it will be classed as a new pension contribution.
Director Alan Smith says: “In 2012, people with enhanced protection who are still working will be auto-enrolled into personal accounts and unless they act quickly and opt out they will lose this protection and benefits valued over the lifetime allowance will be taxed at 55 per cent.
“The resulting tax bill could potentially run to tens of thousands of pounds.”
Informed Choice director Martin Bamford says: “It is definitely a risk, particularly because a lot of people will have registered for enhanced protection a long time ago and forgotten about it. It is good this is being flagged up. Hopefully, the Government will exempt this.”