It is estimated that around 237,000 pensioners have been underpaid around £1.46billion according to data shared by the DWP.

There are six particular groups strongly encouraged to contact the Pension Service to see if they could be entitled to more state pension.

Women who retired under the old state pension system are those said to be mainly affected as they may not have received the state pension payment they were owed under their husband’s National Insurance records.

Commenting on the most recent figures, Helen Morrissey, head of retirement analysis at Hargreaves Lansdown, explained there is still a long way to go as the situation will not be resolved soon.

She warned: “In the meantime, thousands of pensioners are getting less than what they are entitled to.”

Who may be due back payments for state pension?

The following people may be due state pension back payments:

• Married women whose husbands turned 65 before March 17, 2008 and who have never claimed an uplift to the 60 percent rate
• 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
• Over-80s who are receiving a basic state pension (also called a Category D State Pension).
• 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

Ms Morrissey said: “DWP is making progress in dealing with state pension underpayments but there’s a mountain still to climb.

‌“So far almost 47,000 underpayments have been identified with £300million being repaid.

“However, with estimates suggesting as many as 237,000 pensioners have been underpaid £1.46billion, it is clear this is a situation that is not going to be resolved any time soon and in the meantime thousands of pensioners are getting less than what they are entitled to.”

She continued: “The issue mainly affects women retiring under the old state pension system (Basic).

“Some were unaware of the problem but many who queried the issue with DWP over the years were told there was no issue with many enduring real financial hardship as a result.

“These women have been let down on a gigantic scale and need resolution as soon as possible.”

Anyone who thinks they must be affected can call the Pension Service on 0800 731 0469.

A DWP spokesperson previously 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.”

The DWP released figures in November 2022 showing that 31,817 underpayments had been identified and £209.3million repaid to claimants.

However a new progress update is due to be published on May 11, but it is estimated that as many as 237,000 pensioners have been underpaid around £1.46billion.

For more information, people can visit the Government website.