This group would have expected to qualify for their pensions at the age of 67, but they will now have to wait until they reach 68, as the date for raising the pension age is brought forward by about ten years.
Pension analyst Tom McPhail, of Hargreaves Lansdown, has estimated that 10 million will be affected on the basis that around 1 million people are likely to be retiring each year.
The pension age is being increased in stages as life expectancy rises, with a pension age of 66 starting in October 2020 and 67 being phased in between 2026 and 2028.
The move to 68 had been pencilled in for people retiring from 2044, but George Osborne said the date would be brought forward to the mid-2030s.
It will rise to 69 in the "late 2040s", he added.