Applications for pension credit – allowing low-income pensioners to also receive winter fuel payments – have seen a sharp rise since the government announced cost-cutting plans.

Chancellor Rachel Reeves has withdrawn the fuel payments from 10 million pensioners, to help cover what she called a £22bn black hole in the public finances.

The decision announced in July has led to 150,000 applications for pension credit being submitted since, according to the Department for Work and Pensions (DWP).

But only 42,500 have been successful, with thousands being rejected and others awaiting a decision.

Most people will be eligible for the new, means-tested winter fuel payment only if they have registered first to receive pension credit.

Some 150,000 applications for pension credit have been submitted in the 16 weeks since July 29, when the chancellor made her announcement.

That was a 145% increase compared with the previous 16 weeks. However, the number of people being awarded pension credit has only increased by 17% over the same period.

The high number of rejections could be people failing to meet the criteria, or failing to submit the 24-page, 223-question form properly.

The number of new applications represents a small fraction of the 880,000 pensioners estimated to have been eligible for the benefit but who had not put in a claim.

Those who apply before 21 December will receive backdated payments of both pension credit and the winter fuel allowance, and the DWP has deployed 500 extra staff to handle claims for the benefit.

Pensions minister Emma Reynolds said: “We’re pleased to see more pensioners are now receiving pension credit and our staff are processing claims as quickly as possible.

“With December 21 approaching, my message is clear: check if you are eligible for pension credit and if you are then apply, as it unlocks a range of benefits including the winter fuel payment.”

However, campaigners and opposition parties have been critical of delays.

The government’s own data suggests a 10-week typical wait between an application being submitted and a final decision.

Liberal Democrat Treasury spokesperson Daisy Cooper said the figures were a “damning indictment of the government’s failure to protect pensioners this winter”.

“Millions of vulnerable pensioners are still set to lose their winter fuel payment just as the cold weather bites,” she said.

Shadow work and pensions secretary Helen Whately said the “stark reality” was that hundreds of thousands of eligible pensioners would miss out.

The changed winter fuel payment policy remains under continued scrutiny. The Unite union is pushing ahead with legal action aimed at overturning it.

In Scotland, ministers announced extra measures to help those set to miss out.

An estimated 880,000 low-income pensioner households eligible for pension credit currently fail to claim it.

The government says it is worth an average of £3,900 a year and claiming it can qualify people for other financial support such as winter fuel payments.

You can check your eligibility for pension credit via the government’s online calculator.

Information is also available on how to make a claim. There is also a phone line available on weekdays – 0800 99 1234.

There is a guide to benefits, when you qualify and what to do if something goes wrong, provided by the independent MoneyHelper website, backed by government.

Benefits calculators are also run by Policy in Practice, and charities Entitledto, and Turn2us.