Older married women may be owed a share of £100m ($121.66m) underpaid state pension contributions.
An investigation by former pensions minister Sir Steve Webb has revealed about 130,000 female retirees could be missing out on a bigger state pension due to government errors.
Some retired married women can collect a state pension based on their husband's work record but many are receiving less than they should, reports This Is Money.
It is a double blow for the 3.8 million women born in the 1950s who were made to wait up to six years for their state pension when the government raised the age from 60 to 66.
The latest scandal affects married women who reached state pension age before April 2016.
These women are entitled to 60% of the state pension their husband gets. This is due to their working life being at a time when more wives were financially dependent on their husbands. In many cases women did not pay enough National Insurance contributions to earn a full pension.
Before 2008, married women had to claim the extra income themselves when their husband started collecting his pension but from then onwards, the DWP was supposed to pay the upgrade automatically.
But figures suggest around 130,000 married women – whose husbands were collecting the full basic state pension of £134.25 a week – were getting pensions lower than the £80.45 a week they should receive.
Sir Steve, a former Lib Dem MP, told the Daily Mail: "It is truly shocking that thousands of women are being short-changed on their state pensions. The system is highly complex and few will be aware of the special rules for married women.
"It is time for the DWP to take this issue seriously and launch a full investigation."
He said widows and divorcees could also be missing out because they were also entitled to a pension rate based on their husband's contributions.
A DWP spokesman said: 'We are aware of a number of cases where individuals have been underpaid state pension. We reimbursed those affected as soon as errors were identified.
"We are checking for further cases, and if any are found awards will be reviewed and any arrears paid."