Hundreds of thousands of state pensioners are still waiting for refunds due to "shocking" delays from the Department for Work and Pensions ( DWP ).
The latest figures from the DWP show it has underpaid 237,000 state pensioners a total of £1.46billion.
So far the DWP has paid out £209million to almost 32,000 people - just 13% of underpaid pensioners.
More than a billion pounds is still outstanding.
The repayment process was meant to finish by the end of 2023, but the deadline has now been pushed back to late 2024.
Sir Steve Webb, partner at consultants LCP and former pensions minister, said: "T he scale of these underpayments is so great that putting it right could easily end up taking four years or more from start to finish.
"It is quite shocking that well over a hundred thousand pensioners are to this day receiving the wrong rate of pension, and the DWP is clearly way behind schedule in fixing the problem.
"With cost of living pressures affecting many elderly people on low incomes, it is essential that the pace of fixing these errors is stepped up and people get the money they are due as soon as possible."
Affected pensioners can include widows and widowers, divorcees and more. Retirees can be underpaid the state pension for a number of reasons.
The main three groups being underpaid are:
- Married women, who should have received an upgrade to a 60% basic state pension when their husband retired
- Widows (and widowers) who should have inherited an enhanced state pension when their spouse died
- Over 80s already getting a state pension when they turned 80, who should have been automatically upgraded to a 60% basic state pension
Hargreaves Lansdown senior pensions and retirement analyst Helen Morrissey said: " The DWP has let pensioners down on a massive scale – particularly women who tend to retire on lower incomes anyway.
"In some cases, these underpayments have stretched back decades and even though DWP has pledged to hire more people to speed up the process, it is clear many could be waiting for some time still before they are reunited with their money."
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."
How to check if you have been underpaid the state pension
These refunds are for errors the DWP has spotted and is correcting itself.
But if you think you may not be getting the full amount you are entitled to from your state pension you should contact the Pension Service.
Make sure you have your National Insurance number to hand when making your claim, along with details of what you currently get in state pension.
If applicable, also have your spouse or civil partner’s name, date of birth and death, their National Insurance number and how much your spouse receives or did receive in state pension.
