London, Jan 22 (IANS): The British government's Department for Work and Pensions (DWP) estimates that it has underpaid 134,000 pensioners, mostly women, over 1 billion British pounds ($1.36 billion) of their state pension entitlement.

The House of Commons Public Accounts Committee (PAC) said that in a report on Friday. Some errors date as far back as 1985.

"The errors, which mostly affect widows, divorcees and women who rely on their husband's pension contributions for some of their pension entitlement, happened because of the department's use of outdated systems and heavily manual processing. Small errors that were not recognised each time added up over years to significant sums of money," the report added.

Meg Hillier, Chairman of the PAC, said an unknown number of pensioners died without ever getting what was due to them, Xinhua news agency reported.

Fixing the DWP's mistakes is expected to cost taxpayers over 24.3 million British pounds in staff costs alone by the end of 2023, the report said.

With experienced, specialised staff moving away, the DWP is already experiencing backlogs in processing new applications, the report added.

Describing the long-term underpayment of state pensioners as a "shameful shambles," Hillier said, "For decades, the DWP has relied on a state pension payment system that is clunky and required staff to check many databases -- and now some pensioners and the taxpayer are paying in spades."

She added that there was no assurance the errors that led to the underpayments in the first place will not be repeated in the correction exercise.