Millions of ‘WASPI women’ have been told they will not receive compensation over state pension changes – you can see how much you may have missed out on with our interactive gadget.

The Parliamentary and Health Service Ombudsman (PHSO) said women born between April 1950 and April 1960 were “owed” money because increases in the state pension age, from 60 to 66, were not communicated properly.

Some women were notified of the change to their pension age less than a year before they had been expecting to retire at 60, which left them without enough time to adjust their savings plans, the ombudsman found.

The report also said the 3.6 million women affected should have received a letter informing them of the changes up to four years earlier than they did.

Work and Pensions Secretary Liz Kendall said the government accepted the Ombudsman’s findings of maladministration and apologised to 1950s born women for a 28 month delay in writing to them. But she ruled out compensation payouts.

Ms Kendall claimed most women knew the state pension age was increasing, and argued the failure to send out letters wasn’t “as significant as the Ombudsman says”.

She said: “The alternative put forward in the report is for a flat rate compensation scheme, at level four of the Ombudsman’s scale of injustice, this would provide £1,000 to £2,950 per person at a total cost of £3.5 billion and £10.5 billion.

“Given the vast majority of women knew the state pension age was increasing, the Government does not believe paying a flat rate to all women at a cost of up to £10.5 billion would be fair or proportionate to taxpayers.”

If you are a woman born between April 1950 and April 1960, you can use this interactive tool to see when the ombudsman says you should have been notified of the changes to your pension, and how much you could have been entitled to.

A decade has passed since the Women Against State Pension Inequality campaign group – or WASPI for short – launched a campaign for compensation.

It led to a five-year investigation into alleged failures at the Department for Work and Pensions (DWP).

The PHSO used a severity of injustice scale to determine a financial payment that it believes is appropriate and proportionate. The scale has six levels of payment and PHSO has recommended a Level 4 payout of between £1,000 and £2,950 to recognise the “significant” and “lasting impact” suffered by many women.

Had the government agreed to that compensation level, it could have meant a total cost to the taxpayer of between £3.5 billion and £10 billion.

WASPI campaigners, however, demanded compensation payouts at Level 6, which is £10,000 or more. That would potentially mean a bill of £36 billion for the government.