Around 165,000 older people have been underpaid their state pension by £1.2 billion due to historical system errors.

The Department for Work and Pensions (DWP) say the errors affect mostly married women, widows and those aged over 80.

Retirees could be owed up to £11,650 in back payments as the State Pension LEAP (Legal Entitlements Administrative Practice) exercise remains on schedule to be finished by the end of 2024.

The DWP also estimates that 210,000 people may have been underpaid another £1.3billion due to historical issues relating to Home Responsibilities Protection (HRP).

The issues affect mostly women who received Child Benefit before 2000 and whose National Insurance record was not updated to reflect periods of HRP they were entitled to.

A total of 10 million National Insurance records of people claiming Universal Credit have not been updated properly which means a small proportion of these may have also been underpaid their State Pension.

Anyone affected will receive a letter from HMRC this Autumn.

Between January 2021 and the end of March 2023 the DWP has identified 50,569 underpayments, with people owed a total of £324million.

There are six specific groups which are being urged to contact the pension service to check their state pension payment.

Married women whose husband turned 65 before March 17, 2008, and who have never claimed an uplift to the 60 per cent rate and widows whose pension was not increased when their husband died.

Widows whose pension is now correct, but who think they may have been underpaid while their late husband was still alive, particularly if he reached the age of 65 after March 17, 2008 and those over 80 who are receiving a basic State Pension of less than £80.45.

Widowers and heirs of married women where the woman has now died but was underpaid state pension during her lifetime.

Divorced women, particularly those who divorced after retirement, to check that they are benefiting from the contributions of their ex-husband.

The Basic State Pension which retirees can receive is up to £156.20 each week and the New State Pension up to £203.85.

A DWP spokesperson said: “The action we are taking now will correct historical underpayments made by successive governments.

"We are fully committed to addressing these errors, not identified under previous governments, as quickly as possible.

“We have set up a dedicated team and devoted significant resources towards completing this, with further resources being allocated throughout 2023 to ensure pensioners receive the support to which they’re entitled."