In your 20s? You may have to wait 50 years for a pension: Biggest shake-up for a century to be unveiled by Osbourne The move will slash Britain's annual state pension bill by £400billion Age which people can claim their pension will be linked to life expectancy Anyone currently in their 40s or younger will be affected by the moves A baby girl born today may not get her state pension until the age of 77 Controversial: Anyone currently in their 40s or younger will be affected by the move announced by George Osborne Young people currently in their 20s could be forced to work until their 70s, under a radical shake-up of the state pension system which will be revealed today by Chancellor George Osborne. In the biggest change for a century, the age at which a person can begin to claim their state pension is to be linked directly to life expectancy. Anyone currently in their 40s or younger would be affected by the move, which will see the state pension age rise as the average person lives longer. Experts predict a baby girl born today, who has a one-in-2.5 chance of living until 100, may not get her state pension until the age of 77. The move will slash Britain's state pension bill, by an estimated £400billion over a 50-year period. Plans to raise the pension age to 67 by 2028 will not change, but under the new rules the age is expected to reach 68 by the mid 2030s - much earlier than had previously been predicted. The pension age will be set by an independent expert commission which will review the latest official statistics every five years. As a result of the changes, people from different generations can expect to spend broadly the same proportion of their lives contributing to the state pension as receiving it. In 1952, a man reaching state pension age spent around 21 per cent of his adult life in receipt of the state pension. This had risen to roughly 24 per cent by 1980, 30 per cent by 2000 and 32 per cent by 2010. The new system being announced today will maintain the ratio at a third, and prevent it from rising any further. At present, a man can start to claim his state pension from the age of 65 and a woman from 61 and nine months. Both state pension ages are already set to increase, and these dates will not change under the proposals, which will be announced in today's Autumn Statement. This means those currently in their 50s and 60s will not see a change to the age at which they can expect their state pension. By 2018 it will be 65 for women as well as men, and will continue increasing for both to 66 in 2020, 67 by 2028 and will keep rising. Under current estimates of life expectancy, it will rise to 68 in the mid-2030s from its current predicted date of 2046, rising to 69 by the late 2040s. Future: David Cameron said the changes were part of a long-term plan Reform of the state pension, Mr Osborne argues, has become more urgent as people are living longer, healthier lives. After the Second World War, the UK state pension age was set at 65 for men, at a time when a man's life expectancy was just over 66 and a woman's was just over 72. Over the past 100 years average life expectancy beyond the age of 65 has almost doubled, rising by just over ten years for both men and women. The number of people surviving until they are 105 and above has almost doubled in less than a decade, official figures show. At present there are 610 people in this age group, compared with 320 a decade ago, according to the Office for National Statistics. Overall, 12,320 people are aged 100 and above. The plan will trigger controversy due to huge regional differences in life expectancy, as well as concerns about how much of their retirement will be spent in good health. A woman of 65 in East Dorset will typically live 23 more years and eight months. In Corby, she is likely to live for only another 18 years and seven months. In a Lords debate on Tuesday, Labour peers called for future rises in the state pension age to be regionalised, but the proposals were rubbished yesterday. Tom McPhail, head of pensions research at financial advisers Hargreaves Lansdown, said: "They are absolutely unworkable. What's to stop people moving house? Speaking on a visit to China, David Cameron called them the next steps in a "long-term plan."