Suppose someone currently receives:

• DB pension: £20,000 a year
• State Pension: £12,000 a year
• Total: £32,000

A 40% DB reduction would mean:

• DB: £12,000
• State Pension: £12,000
• Total: £24,000

That's a £8,000 annual reduction, or £667 a month before tax.

For someone receiving £30,000 DB, the reduction would be £12,000 a year.

This is the crucial distinction.

A DB pension promises an income according to the scheme's rules - usually based on salary and years of service. The investment and longevity risks largely sit with the scheme/employer.

With DC, the individual accumulates a pot. The eventual income depends on contributions, investment performance and how the pot is subsequently converted into income.

So if a person has:

£20,000 DB income

you can't simply say:

'A comparable DC pension produces £12,000, therefore reduce the DB to £12,000.'

You would need to establish the capital value required to produce the same income over the person's expected lifetime, including inflation protection, survivor benefits and investment risk.

The really interesting question is what would happen to the UK

If your proposal is essentially:

'People with generous DB pensions should have their income reduced by 40%, bringing their retirement income closer to what people with DC pensions receive.'

then there would be several major effects.

This would affect people who had already retired and, depending on the legislation, potentially people who had already earned their DB entitlement but hadn't retired.

For example:

That would represent a very large transfer of income away from DB pensioners.

This is particularly important.

If someone's DB income were reduced sufficiently, they could become eligible for Pension Credit or other support, depending on their circumstances.

Consequently, the government wouldn't necessarily save the full 40% reduction.

It could recover some of the saving through increased taxation or reduced benefits, but some people would move in the opposite direction and require more means-tested assistance.

This is probably the biggest obstacle.

People who paid into a DB scheme generally did so on the understanding that they had earned a particular pension under the scheme's rules.

Reducing accrued benefits retrospectively would therefore raise major legal and constitutional questions.

It would be very different from changing the pension arrangements for future service.

For example:

Existing entitlement

'You have earned £20,000 a year.'

versus

Future entitlement

'From 2027 onwards, your pension accrual will be less generous.'

The second is much easier to design prospectively.

There is another way of looking at the proposal

Rather than cutting DB pensions, you could ask:

That is a legitimate policy question.

The answer is that Britain has already moved substantially in that direction.

DB schemes have declined dramatically in the private sector, while DC schemes have become the dominant form of workplace pension for new private-sector workers.

And interestingly, the government itself acknowledges the problem you're identifying: its 2025 analysis projects that future retirees will generally have lower private pension incomes as DB provision declines before DC pensions have had time to build up sufficiently.

It estimates that private pension income for people retiring in 2050 could be 8% lower than for those retiring in 2025, on its modelling assumptions.

So the problem isn't necessarily that DB pensions are 'too generous'.

It may instead be that DC pensions aren't generous enough.

There is a particularly interesting alternative

Rather than reducing DB pensions by 40%, you could establish a common retirement-income framework.

For example:

Existing DB

Leave accrued DB rights alone.

Future DB accrual

Gradually reduce the accrual rate for future service.

Increase minimum employer/employee contributions and improve investment arrangements.

At retirement

Give DC savers access to a collective pension arrangement that provides income for life.

This is actually an area the government is now developing. The new Retirement Collective Defined Contribution (CDC) model is intended to pool DC assets and provide a lifetime income, rather than leaving individuals entirely exposed to the risks of managing their own pension pot.

That is potentially much closer to what you're getting at: make the retirement system more comparable rather than simply cutting one group of pensioners.

And there is a very important generational issue

Someone who retired with a DB pension may have had:

Employer DB contribution + employee contribution -> guaranteed pension

whereas a younger worker may have:

Employer contribution + employee contribution -> investment pot -> uncertain retirement income

The younger worker carries considerably more investment and longevity risk.