Millions of people currently in their twenties may have to work until they are 70 before receiving a state pension, a former minister has said.

Documents produced by the Department for Work and Pensions (DWP) reportedly suggest a “more aggressive” timetable for raising the state pension age, which could take it higher than ever before more quickly than previously expected.

Tens of millions of workers aged 30-45 and 45-55 could also have to work for longer before retiring, until they are 69 and 68 respectively.

The earliest age at which someone can start receiving their state pension is now 65, but on the current timeline it is due to rise to 66 between 2018 and 2020, to 67 between 2026 and 2028, and then to 68 between 2044 and 2046.

An official review is currently taking place into the future of the state pension and on 16 November the DWP asked the Government Actuary’s Department to look at the impact of projected life expectancy in future years. It asked the department to set out a schedule for state pension age increases, based on the previously announced policy that people should spend two-thirds of their adult life working and one third in retirement.

But the DWP sparked speculation that it would raise the retirement age out of keeping with changes to life expectancy, by also requesting figures for people spending 32 per cent of their adult life in retirement.

The DWP said this “reflects the experiences of those reaching state pension age over the last 20 years”, but former pensions minister Steve Webb refuted this, saying it failed to take into account more recent improvements in longevity. He said that asking for figures based on 32 per cent was an “unexpected move”.

Analysts at Willis Towers Watson also said the surprise move suggested that a further increase of the state pension age could be on the cards, and used official life expectancy projections to work out what exactly this could mean. The analysts said people born between March 1962 and April 1972 would see their pension age rise from 67 to 68. Meanwhile, those born between March 1973 and April 1985 would have a pension age of 69, rather than 68. Those born between March 1986 and April 1994 would see their retirement age rise from an assumed 69 to 70.

Mr Webb has called on the Government to “come clean” about its intentions, so that people can start to prepare for a working life of up to 52 years.

Mr Webb, who is now director of policy at mutual insurer Royal London, said: “The previous policy strikes a fair balance between expecting people to work longer and allowing people to enjoy a decent retirement.

“If the Government is planning to force tens of millions of people to work to 68, 69 or even 70, then it should be transparent about its plans. This would be a huge shift and should be properly debated, not buried in a technical document seen only by specialists.”

David Robbins, a senior consultant at Willis Towers Watson, said it made sense for the government to target pensions as an easy way to save money, especially because in the past there was little public dissent when age rises were announced.

“If the Government needs to shore up the public finances, it would struggle to find a more politically painless way to take £8,000 off tens of millions of people,” he told the Daily Express.

“News that the state pension age will rise to 67 by 2028 barely generated a squeak of protest.

“Maybe people never believed the state pension promise anyway, or maybe it is just too far away to worry about.”

He added: “Starting the increase to 68 as soon as the state pension age hits 67 means it will happen in time to catch the big bulge of future pensioners born during the mid-1960s baby boom. A higher pension age will also boost tax revenues if people respond by staying in work.”

Mr Webb said: “The Government is for the first time paving the way for people in the workforce up to the age of about 30 to have to work until they are 70.”

He pointed out that possible future changes to state pension entitlements were hinted at by the chancellor Philip Hammond in his autumn statement, when he said: “As we look ahead to the next parliament, we will need to ensure we tackle the challenges of rising longevity and fiscal sustainability.” This raises for the first time the prospect of pensioners’ benefits no longer being ringfenced after 2020, and being cut as part of the Government’s austerity measures.

This was “an additional indication that a more aggressive approach on the state pension age seems likely”, said Mr Webb.

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There are also fears that the Government will water down the state pension “triple lock”, which means that the payments rise in line with average wages, inflation, or 2.5 per cent – whichever is the highest.

Damian Green, the minister responsible for pensions, did not guarantee this mechanism would remain during an interview on ITV on Sunday, saying it was “premature” to decide on its future. “We’ll need to see what happens to the economy between now and 2020, apart from anything else,” he said.