The bereaved parents were invited to reimburse the state’s pensions that were wrongly sent to the people who died by the Department of Labor and Pensions (DWP).
The DWP confirmed that it had no legal right to recover the money, but argues that it does it to protect public funds.
Former Minister of Pensions, Sir Steve Webb, said that the letter sent by the ministry to families does not clearly show that reimbursements are voluntary.
Over the past five years, the DWP has mistakenly paid more than 500 million pounds of state pensions and pension credits to the deceased, recovering about half of bereaved parents.
This situation may occur if there is a delay in the declaration of a death – or in the treatment of the DWP – causing the additional pension program.
Consequently, part of this payment can cover a period after the death of the person.
In the past year, 144 million pounds sterling have been paid too much in state pensions by the DWP after the death of a person due to a delayed report.
The Department has recovered 67.3 million pounds sterling, leaving 76.7 million pounds in the overpayed in the not recovered.
Sir Steve, who is associated with Consultancy LCP Pensions, used a freedom of information to see a copy of the letter that DWP sends to families and testamentary executors.
He revealed that even if the ministry requests that money has returned to protect public funds, it does not stipulate that the reimbursement is voluntary.
The former minister said he was “shocked” to learn that the letter does not specify that the return of money is not compulsory.
Sir Steve argued that this transforms retirement reimbursements into a “lottery” where some people return the money while others do not do so.
The former liberal democratic politician, who sat in the ministry between 2010 and 2015, warned that the system affects the most vulnerable disproportionately, who can be in mourning and unable to question the letter.
He called for a “coherent approach”, urging the government to guarantee a legal basis to recover the overpaye or stop benefiting from “people who do not know how this system works”.
Radio auditor 4 Money Box, Dennis, said that he had been “caught up” by the procedure twice, after the death of his two parents.
Dennis explained that he had followed the instructions of the letter to “settle all” the affairs of his parents.
He added that he “obeys the government and will pay it” because he did not know that the refund was not legally necessary.
Another Money Box listener, Jan, told the BBC that his late husband would be “absolutely next to it” if he knew that more than £ 250 of his pension had been reimbursed when he did not need.
Jan said she was confused when she received a DWP letter declaring that her husband had been too paid because she had informed them “immediately” after her death.
“It was overwhelming the way it happened and (the way) everything went,” she said.
The Department of Labor and Pensions said in a press release: “It is not our intention to cause distress, however, we have the responsibility of taxpayers to recover the overpaye. We recognize that it is not always possible.
“Although there is no legal obligation to repay a debt of this type, we recognize that some people will be ready to reimburse money to which there was no right. We provide full contact details and encourage Anyone disturbing to call us. “
To find out more about this story, listen to Money Box at 12:00 p.m. GMT on BBC Radio 4 or catch up on the BBC.