This April, the triple lock will see the full new state pension increased again, by 4.8% to £241.30 per week, in line with wage growth. The expensive DWP increases cost the taxpayer billions, with more than 5% of the UK’s GDP spent on pensions, or £146.1 billion.

As a result, speculation has ramped up in recent years that the triple lock’s days could be numbered, despite Labour’s pledge to keep it until at least the next election.

This week, campaign group the Civil Service Pensioners’ Alliance (CSPA) is sounding the alarm over the triple lock.

The CSPA says the state pension is ‘the single largest source of income for most retirees’ and that if the triple lock wasn’t in place, it would cause ‘widespread hardship’.

The group warns it is ‘critical’ to maintain the inflation basis of the triple lock to prevent a ‘resurgence of pensioner poverty’.

It says: “Before the introduction of the triple lock in 2011, the value of the State Pension had been eroded significantly relative to earnings, dropping from 26% of average earnings in 1980 to 16% by 2010. The triple lock has since reversed this, raising the pension’s value to nearly 25% of average earnings by 2022 and reducing pensioner poverty from around 15-20% in the late 1990s to 10-12% by the mid 2010s.

“It is critical to maintain the triple lock’s link to inflation and establish a clear, stable relationship between the State Pension and average earnings to prevent a resurgence of pensioner poverty.

“The Institute for Fiscal Studies agrees with the Pensions Commission’s recommendations to guarantee a stable, earnings-linked State Pension, implement gradual reforms to the triple lock, avoid means-testing, and carefully manage pension age increases to protect pensioner income and reduce inequality.

“It is worth noting that two-thirds of today’s pensioners receive the lower Basic State Pension, which applied before 2016. These pensioners are more likely to be in poverty.”

The group, which campaigns on the civil service pensions in particular, added: “We propose: The protection of the triple lock extends beyond 2029, ensuring pensions rise in line with living costs and wages.

“To defer further SPA rises until inequalities in life expectancy narrow and a new settlement is agreed.”

In November, Conservative MP Sir Edward Leigh told Parliament that the triple lock is ‘unsustainable’.

He said: “We all know that the triple lock is unsustainable. You cannot have a situation where people of my generation are consuming an ever-greater proportion of national wealth through the state pension.

“Frankly, our government never dared tackle it having brought it in because they knew that the Labour Party would crucify them at the ballot box.

“Now the Labour Party is caught in the same bind.

“The fact is, it is completely unfair on younger people if the burden of older people, through the triple lock, increases year by year.”

Conservative former minister Tom Tugendhat said there are not “enough young people for an aging population”.

He told MPs: “The honesty is the demographics of this country are going against us. That means, I’m afraid, we do need to look at the triple lock.

“I have already been clear. Now, I know my front bench doesn’t agree with me, but I have been clear on this, that we simply cannot afford the level of welfare payments that we are making.

“We need to be clear that health and pensions are now costing too much.”