About 200,000 women could be due around £13,500 each, after an investigation found state pension administration errors that date back decades.

A joint investigation by This is Money pensions columnist (and former Pension Minister) Steve Webb and journalist Tanya Jefferies, found there was a failure to pay automatic increases to the state pensions of wives, widows and the over-80s who hit state pension age before April 2016 and should have qualified for boosted payments due to their husband’s National Insurance record. Some of the affected women received pensions of as little as 86p a week, when they were in fact entitled to 60% of the basic state pension – about £80 a week.

A team of 155 civil servants is working to trace every woman affected and pay them any money owed. But the task could take six years and recent Budget documents revealed that it is likely to cost the Department for Work and Pensions (DWP) around £3billion to rectify.

Those affected include the following:

• Married women whose husband turned 65 before 17 March 2008 and who have never claimed an uplift;
• Widows whose pension was not increased when their husband died (they can potentially receive a full basic State Pension, plus a percentage of their late husband’s additional State Pension);
• Widows whose pension is now correct, but who may have been underpaid while their husband was still alive, particularly if they reached 65 after 17 March 2008;
• Women over the age of 80 who are receiving a basic pension of less than £80.45, provided they satisfied a basic residence test when they turned 80;
• Widowers and heirs of married women, where the woman has died but was underpaid the State Pension during their life, especially when their husband turned 65 after 17 March 2008;
• Divorced women, particularly those who divorced after they retired, who need to establish whether are benefitting from the contributions of their ex-husband.

Labour Pension Commission Chairman Stephen Timms MP has asked the DWP to explain how payments will be prioritized - whether payments will be made in the order of age or unpaid amount for example and how the heirs of those who died will be contacted.