She was responding too a report published this week by the Centre for Social Justice, a think tank headed up by ex-Tory leader and former Work and Pensions Secretary Iain Duncan Smith, which suggested the State Pension age should rise to 75.
The intervention marks another spat between the two former DWP colleagues, after Baroness Altmann criticised Mr Duncan Smith in newspaper interviews last year, claiming he refused to listen to her concerns over equalising the pension age for men and women when they were in Government together between 2015 and 2016.
Referring to the report Baroness Altmann said: “The Centre For Social Justice has just released an astonishing policy paper, proposing to increase the State Pension Age dramatically - to 70 by 2028 and then to 75 a few years later.
“Apart from the fact that we are already seeing problems as women's State Pension Age has risen sharply, and further increases for men and women are already underway, these proposals would create significant social 'injustice’.”
She added: “Stark pension age rises would create significant hardship for many Britons.
“Such misguided policy proposals suggest little understanding of the role and impact of State Pensions and the differentials within our society.”
She said raising the age would also hit those who had had manual labour careers and would remove eligibility to other benefits.
The former minister concluded: “Such changes impact people's lives and constant tinkering is damaging.
“Ideally, nobody should have an expectation of any specific age at which they stop work altogether.
“Just running pensions policy on the basis of averages is not appropriate in today's Britain.
“Planning for part-time work and ongoing retraining through life will be important to help people work longer, but the inflexibility of a fixed pension age fails to cater for individual differences.”
The CSJ report claimed working until 75 would “remove barriers for older people”.
It added: “While this might seem contrary to a long-standing compassionate attitude to an older generation that have paid their way in the world and deserve to be looked after, we do not believe it should be.
“Working longer has the potential to improve health and wellbeing, increase retirement savings and ensure the full functioning of public services for all.”