It has been revealed that almost 900,000 Brits claiming their pension are missing out on a cash boost worst as much as £11,300 a year.

Called Pension Credit, this historically under-claimed Department for Work and Pensions (DWP) benefit has seen the number of claimants explode in recent weeks.

The number of people applying for the benefit, which can top-up your monthly income to a minimum level, has skyrocketed in the wake of Chancellor Rachel Reeves' decision to axe the universal Winter Fuel Payment.

The £300 seasonal cash payment will now only be paid to people in receipt of Pension Credit, as the new Labour government tries to fix an inherited £22 billion "hole in the public finances."

This has caused a huge uptick in claimants for the benefit, which the DWP has struggled for years to get low-income pensioners to take up.

In the five weeks after Reeves' announcement, the number of poorer pensioners applying for the benefit has more than doubled, with 38,500 new applications.

This represents a 115 percent increase in potential claimants, many of whom will get weekly pension payments under £218.15 if they are single, or £332.95 for couples. Across a year, Pension Credit can be worth as much as £11,300 per person.

This is a major turnaround for the benefit that Martin Lewis often describes as "chronically under-claimed."

The personal finance guru has urged low-paid pensioners to ring the Pension Credit helpline to see if they qualify, as even those above these thresholds can still sometimes qualify.

The Money Saving Expert reassured: "You will not be told off for asking if you are due Pension Credit. If you're not due Pension Credit, they'll just tell you."

By the end of the week when the Chancellor announced that the Winter Fuel Payment would only be paid to older Brits claiming Pension Credit (July 29), the number of people applying for the cash-boosting benefit jumped from 3,500 per week to 7,900.

A government spokesperson said: "Given the dire state of the public finances we have inherited, it's right that we target support to those who need it most.

"Over a million pensioners will continue to receive the winter fuel payment, while many others will also benefit from the £150 warm home discount from October to help with their energy bills over winter.

"We are seeing increased demand in pension credit claims and continue to urge pensioners to check their eligibility to make sure as many people in need can access this support."

The DWP has also released the data for the five weeks before and after the Winter Fuel Payment cut, showing that uptake of the historically under-claimed benefit has remained high after the announcement. The figures were rounded by the department.

You can find out more information about claiming Pension Credit on the government website.