In one case a woman was paid more than £7,000 in arrears but had previously been told all was well despite phoning to query her payments.
The Department for Work and Pensions (DWP) anslår at det er underbetalt 134,000 pensioners and those it can trace will be paid an average of £8,900.
De National Audit Office (NEI) said repeated human errors were almost inevitable amid complex rules and outdated IT systems.
The NAO’s report into the mistakes highlighted how Sir Steve had approached the DWP with examples of underpayments.
Sir Steve, who is now a partner at consultants LCP (Lane Clark & påfugl), said he had helped one couple in their 70s from the Midlands.
Irene Wise, 74, pensjonert seg i 2007 and had a reduced pension because of her national insurance record.
Her husband retired in 2013 and claimed his pension. At that point Mrs Wise’s pension should have been increased to the married women’s rate, but this did not happen.
Following recent publicity she contacted Sir Steve, who raised her case with the department.
It agreed she was underpaid and she was paid more than £7,000 in arrears.
Sir Steve said: “What is shocking about Mrs Wise’s experience is that she actually rang up to query her pension and was told that all was well.
“I have heard similar stories on too many occasions. Even more worrying is that the new NAO report shows that even when it comes to correcting past errors DWP are still making mistakes.
“It is absolutely vital that the highest standards of quality control are now applied both to the correction of past mistakes and to the information that is given out to people who get in touch.”
A Department for Work and Pensions (DWP) spokesperson said: "Vi er fullt forpliktet til å sikre at de historiske feilene som har blitt gjort av påfølgende regjeringer blir rettet, og som denne rapporten erkjenner, vi bruker mye ressurser på å gjøre det. Alle som blir berørt vil bli kontaktet av oss for å sikre at de mottar alt de skylder.
“Siden vi ble klar over dette problemet, Vi har introdusert nye kvalitetskontrollprosesser og forbedret opplæring for å sikre at dette ikke skjer igjen. ”