Scrapping the state pension triple lock would cut £38bn from Britain’s state pension bill by 2045, a think tank has claimed.

The state pension triple lock – which boosts pensioners’ payments by the highest rate of inflation, wage growth or 2.5pc each year – was introduced in 2011 to guard against retirement poverty.

However, the Intergenerational Foundation (IF) said the mechanism had become unsustainable, unpredictable and unfair to future taxpayers.

Britain is expected to spend £154bn on the state pension this year, rising to £180bn by 2030. The triple lock is expected to cost £15.5bn a year by 2030, according to the Office for Budget Responsibility.

In a new report, the IF proposed only increasing the state pension by inflation until 2030-31 and by the average of inflation and earnings in following years.

It calculated that the changes would save £19bn a year by 2035-36 and £38bn a year by 2045-46.

The IF also argued that 10pc of the savings should be handed back to the poorest pensioners.

Currently, people receiving Pension Credit have their weekly income topped up by up to £238 if they’re single or £363.25 jointly if they have a partner.

However, the IF said they should be awarded a non-means-tested payment of £30 a week, which would also rise each year by the average of inflation and earnings.

Conor Nakkan, the report’s author, said the current system was “fiscally unsustainable” and needed reform.

He said: “The triple lock may have been introduced with good intentions but it has become an expensive and poorly targeted policy.

“It now delivers large increases to all pensioners, including millions who are already well-off, while younger generations face stagnant living standards, high housing costs and a growing tax burden.

The current system is not only fiscally unsustainable, it is also intergenerationally unfair. If the Government wants to protect pensioners from hardship, it should do so directly.”

Sally Tsoukaris, of the pensioner campaign group Later Life Ambitions, said that both measures would leave the poorest pensioners exposed.

She said: “The triple lock is a vital safeguard against pensioner poverty. Older people need security and dignity in retirement, not renewed uncertainty about the value of their state pension.

“Using some of the savings to increase Pension Credit also does not solve the problem. It is means-tested, chronically under-claimed and by the Government’s own figures, close to a million eligible pensioners are already missing out.

“Asking it to carry more of the system would leave too many of the poorest older people exposed.”

Several political figures, including Sir Jeremy Hunt and Michael Gove, have broken cover in recent months to call for the end of the triple lock.

Sir Tony Blair also proposed a raft of reforms, including scrapping the state pension, triple lock and Pension Credit. The former prime minister’s think tank said the changes would save £66bn a year by 2070.

However, the Government has committed to keeping the triple lock in place for the duration of this parliament and no major political party has pledged to scrap it.

A Treasury spokesman said: “By keeping the triple lock, 12 million pensioners will see their income rise by up to £470 this year, and they continue to benefit from the highest personal allowance in the G7.”