Those who want a “comfortable” retirement need more than half a million pounds to generate the income required. These are staggering sums, especially since they assume savers also qualify for the full new state pension. Those who face a shortfall will have to save even more.

These figures are courtesy of pension specialist Standard Life, based on research by the Pension and Lifetime Savings Association.

The PLSA calculates that retirees need £12,800 a year as a bare minimum, and that was before the cost-of-living crisis.

This would cover the bare essentials plus one week's holiday in the UK. It would not stretch to a car, which most people see as a fundamental need.

The full new state pension currently pays a meagre £10,600, which is £2,200 below the bare minimum required. Many pensioners get a lot less than that.

Generating that extra £2,200 would require around £50,000 of company and personal pensions, or other savings such as cash in the bank or tax-free Isas.

A moderate retirement living standard requires income of £23,300 a year, which is £12,700 more than the maximum state pension and requires a total savings pot of £285,000.

This level of income could cover car ownership and one foreign holiday a year, plus the odd meal out.

To be comfortable, enjoying regular holidays and meals out, you need income of £37,300 a year. That's £26,700 above the state pension and requires a hefty £530,000.

The sums look daunting but at least give savers a target, said Dean Butler, managing director for retail direct at Standard Life. “Individual circumstances will vary and life costs less in some parts of the country.”

So how much do you need to invest each month to hit those targets? The answer depends on how early you start.

Someone who starts investing in a pension or tax-free stocks and shares ISA at 25 has a huge advantage over somebody who waits until, say, 45. That's because their monthly contributions have much longer to compound and grow.

If a 25-year-old invested £100 a month and increased their contribution by three percent a year to keep up with inflation, they would have £427,297 by age 67.

This assumes they invested money in shares generating 6.89 percent a year, which is the average total return on the FTSE 100 with dividends reinvested.

The compounding effect doesn't work half as well for those who start later, though.

A saver who started putting £100 a month away from scratch at 45 would only have £79,637 by age 67, using all the same assumptions.

To generate £427,297 from scratch at age 45, they’d have to invest more than £525 a month, vastly more than a 25-year-old.

Even this may not be enough, because inflation will have eroded the spending power of that money over such a lengthy timescale. In practice, people need to invest even more.

Victoria Scholar, head of investment at Interactive Investor, said the golden rule of investing is to start as early and stick with it. "The first pound you invest is most valuable, because it has longer to compound and growth.”