The briefing, published this week, notes that the State Pension is the single biggest driver of higher welfare spending this Parliament, set to cost £13.8 billion more in real terms by 2029-30.

Replacing the Triple Lock with a smoothed earnings link from next year would save £650 million annually by the end of the Parliament – enough, the foundation says, to double funding for the Youth Guarantee aimed at Britain’s NEETs crisis.

The think tank also questions the Triple Lock’s record on poverty. In the 15 years before its introduction, pensioner poverty fell by 15.8 percentage points; in the 12 years since, it has risen by 2.3 percentage points. The foundation further warns of the policy’s unpredictability, noting that while the OBR projects State Pension spending will rise by £80bn over the next 50 years, the Triple Lock’s ratchet effect means the figure could swing £40bn either way, creating uncertainty for both public finances and retirement planning.

With the New State Pension now worth 30% of full-time median earnings – just below the 31% recommended by the original Pensions Commission in 2003 – the foundation argues the policy has largely achieved its aim. At minimum, it says, the current Pensions Commission should set a target State Pension level beyond which the Triple Lock is no longer required.

Ruth Curtice, chief executive of the Resolution Foundation, described the Triple Lock as “a terribly designed policy” that had proved far more expensive and far less effective than hoped. She argued a smoothed earnings link was the most sensible way to keep pensions rising with living standards, adding that the UK government should “call time on the Triple Lock as soon as possible, and put the savings from doing so to far better use”.

The intervention follows similar calls in recent months from Tony Blair and Jeremy Hunt, and comes ahead of Dr Suzy Morrissey’s imminent review of the framework for setting future State Pension ages, which will inform a wider government review next year.

Rachel Vahey, head of public policy at AJ Bell, said the foundation had added fresh momentum to an increasingly important debate. While acknowledging the Triple Lock’s value in boosting the State Pension, she said the central question was now what the policy was meant to achieve and whether it was sustainable.

With State Pension spending already at £154bn and projected to climb further, she argued ministers “cannot dodge this difficult topic forever” and needed a proper conversation about its long-term future.

Ms Vahey suggested the UK government should first define the income level the State Pension is meant to provide, after which a smoother earnings link could be one option worth exploring to avoid the sharp year-to-year swings seen recently.