The 1995 Pensions Act amended the legislation to eliminate women’s eligibility for the State Pension at the age of 60.
The Ombudsman received a large number of complaints concerning the manner in which DWP conveyed this.
Numerous women stated that they were unaware of the modifications and thus suffered substantial financial loss and mental pain.
PHSO discovered that from 2005 onwards, DWP’s actions to convey the State Pension age were deficient.
Parliament has been presented with the investigative report. It details how DWP failed to make reasonable choices based on available facts and failed to contact with impacted women with sufficient haste.
Amanda Amroliwala, Parliamentary and Health Service Ombudsman CEO, said: “After a detailed investigation, we have found that DWP failed to act quickly enough once it knew a significant proportion of women were not aware of changes to their State Pension age.
“It should have written to the women affected at least 28 months earlier than it did.
“We will now consider the impact of these failings, and what action should be taken to address them.”
Commenting on the report, WASPI’s Chair, Angela Madden / WASPI’s Communications Director, Debbie de Spon said: “Today’s findings reinforce what we, unfortunately, knew all along; that the DWP failed to adequately inform 3.8 million 1950s born women that their State Pension age would be increasing.
“The DWP’s own research showed that women were not sufficiently aware of the changes, yet they failed to act. This inaction had devastating and life-altering impacts on women across the country.
“These women have been waiting for many years for compensation. We cannot wait any longer.
“We are calling on the Government to agree fair and adequate compensation for WASPI women rather than allow what has become a vicious cycle of Government in-action to continue.”
A DWP spokesperson said: “Both the High Court and Court of Appeal have supported the actions of the DWP, under successive governments dating back to 1995, and the Supreme Court refused the claimants permission to appeal.
“In a move towards gender equality, it was decided more than 25 years ago to make the state pension age the same for men and women.”