“The politics here are a nightmare,” said David Sinclair, chief executive of the International Longevity Centre – UK. “The problem is that none of the alternatives to removing the triple lock are going to be popular.”

A return to some model of earnings link is favoured by many economists.

Mr Sinclair said to keep the triple lock, government may have to take on more debt, increase the pension age, raise taxes, or potentially all of the above.

“For government it’s a lose, lose, lose scenario,” Mr Sinclair said.

He said the Labour government “will be terrified about even suggesting a cut to the triple lock” after the outcry over its decision to withdraw the winter fuel allowance from all but poor pensioners.

The government is raising the state pension by 4.1% this April, on a par with average earnings.

A government spokesperson said its commitment to the triple lock was “unwavering” and meant “millions will see their state pension rise by up to £1,900 over this parliament”.

In the Conservative camp, there have been hints of a shift in attitude to pensions.

Speaking on LBC, external, Tory leader Kemi Badenoch said the Conservatives were “going to look at means-testing” benefits, in response to a question about the state pension. Her party later insisted she was not referring to the triple lock specifically.

Also, the shadow chancellor, Mel Stride, has said, external the triple lock was unsustainable in “the very, very long term”.

A Conservative source said Stride’s comments had been taken out of context and the party was committed to the triple lock.