Michael and Sue Rawson, educational toys' manufacturers in Sheffield, have been haranguing the Halifax Building Society with faxes over the past two weeks over what they claim is a "gross injustice" to their daughters.
Under the Halifax's proposals for conversion, their 19-year-old daughter who has an account of over Pounds 100 with the building society and should therefore be eligible for membership, will not receive a windfall.
When the account was opened at their daughter's birth, Mr Rawson said that Halifax staff insisted that her parents' names were put at the front of the account as the child was too young to sign for payments.
Because Mr and Mrs Rawson have their own account, they are only eligible for a single windfall pay-out and because their names have remained on their daughter's account she cannot benefit, even though all the money in the account was given to her as gifts.
Mr Rawson said: "She is a student at Birmingham University and would stand to gain Pounds 800 which I am sure she could make good use of. If we'd known this would happen we would have taken our names off the account years ago. I am sure many other families are in this position."
Because Mr Rawson's name fronts all the accounts, his second daughter, aged 15 and not old enough for membership, also loses out.