Baroness Altmann condemned the idea from the Centre for Social Justice (CSJ), in a paper published this week, to increase the pension age from 65 now to 70 by 2028, and then to 75 by 2035.
She said the move would be a betrayal of hard-working people who had planned and saved for their retirements.
The pension age is already set to increase to 67 by 2028 and to 68 by 2046, but the CSJ, co-founded by former Conservative leader Iain Duncan-Smith, wants to see a faster increase. In a national newspaper column, Baroness Altmann wrote: “Forcing Britons to work until their mid-70s may help to boost the economy by £182 billion a year, but to me the idea is chilling and immoral.
“It is an outrageous betrayal of people who have worked hard, paid their taxes and made their National Insurance [NI] contributions for decades in the expectation that they will receive at least a basic income so they can retire, rather than being forced to labour until they drop.”
Baroness Altmann said the proposal gave rise to the “farcical prospect” that 74-year-olds who could not find work would have to go on the dole.
“More than a million over-50s want to work, but can’t find a job because age discrimination is embedded in the labour market,” she wrote.
“Increasing support for these people, with retraining programmes and employer incentives, should be the first priority before increasing the state pension age.”
The proposal would also likely shorten the life expectancy of those in disadvantaged parts of Britain, she added.
“The better-off, whose employment does not usually entail physical labour, might hope to live well into their 80s with good health,” she said.
“But for people burned out by tough manual work, who tend to have poorer housing, diets, access to healthcare and are at greater risk of ill-health and frailty, death comes much sooner. This is already a grave injustice in our society.
“Driving up the pension age even further makes it worse, particularly for those groups who are statistically more likely to die in their late 60s or early 70s, who will suddenly see the finishing line pushed so far into the distance that it becomes meaningless.”
Baroness Altmann, who was pensions minister from 2015-16, said she had rarely seen a proposal “with the potential to do such damage”.
“The flaws in the thinking must be challenged immediately,” she said.