She suggested increasing the number of qualifying years would be a better solution, or switching the triple lock to a double lock.

Baroness Altmann said that governments have failed to prepare properly for the aging population.

“As pensioner numbers soar due to demographic factors that have been in place for decades, and during a cost-of-living crisis, it cannot be a shock that the bill for state pensions is rising sharply,” she said.

“This was always inevitable and is part of the reason why the state pension age has been increasing. However, that is a simplistic response that ignores the vast differences in health and wealth among older groups.”

She warned that accelerating state pension age (SPA) increases would just plunge more pensioners into poverty, pointing out that as the SPA rose to 66, poverty among 65-year-olds doubled.

Extending means-testing so that wealthy pensioners get nothing is also no solution, is Baroness Altmann’s view.

She said: “When Pension Credit was introduced twenty years ago, aiming to focus spending on the poorest pensioners, it contributed to a collapse in private saving, and rising pensioner poverty. If the State Pension is only paid to those with little or no savings, the average worker may reasonably decide not to bother with pension contributions and just spend all their money, in case they are penalised for it later.”

There are other ways to save money on pensioner spending, which do not risk up-ending the whole edifice of the welfare system, she said.

She suggested increasing the number of years required for a full pension from 35 to, say, 45.

“Currently, just 35 years NI record qualifies for a full new state pension, but this is nowhere near a full working life. Someone who started work at 16, has a full record by age 51, even those starting at 21 can have a full record at age 56.

“If the state pension is a recognition of long contributions to our country, perhaps increasing the number of years required for the full pension to 45 is a better and fairer way to control costs.”

She also suggested changing the “political gimmick” of the triple lock to a double lock.

“The so triple lock promises state pensions will rise by the highest of prices, earnings or 2.5% each year. This has become a totemic political symbol of pensioner protection, however the 2.5% element is a rather arbitrary figure and removing it while inflation and earnings are rising by so much more, can cut long-term pension spending, without undermining the whole system.”

She also suggested rolling all universal additional pensioner benefits into a higher state pension to make them taxable.

“At the moment, all pensioners receive tax-free Winter Fuel Payments and other benefits which, unlike the state pension itself, are not taxable. They are worth far more to well-off pensioners than others, which seems unfair and is hardly a sensible use of taxpayer resources which are under so much pressure.”