Almost 13million retirees get a 4.1% pay rise from today, the first Monday of the 2025/26 financial year.

The state pension triple lock lifts the new state pension to £11,973 for those who get the maximum amount, but millions get thousands of pounds less and many are resentful. It happens every year so what’s going on?

A key reason is that there are two state pensions. Anyone who retired from April 6, 2016, will qualify for the single-tier new state pension, while those who retired before then get the basic state pension.

Under the triple lock, both increase each year either by earnings, inflation or 2.5%, whichever is highest.

The problem is that the basic state pension starts from a lower point. So each year’s increase is worth relatively less, and the gap widens every year.

From today, the new state pension will increase by £470.60 to a maximum of £11,973, while the basic state pension rises just £361.40 to around £9,175.40 a year.

That is a staggering £2,797.60 less.

Which works out as a £53.80 shortfall every week.

The gap between the two pensions has widened by £109.20 in just one year and will continue to widen in future.

Stephen Lowe, director at the retirement specialist Just Group, said many see this as unjust. “Retiring just one day before April 6, 2016, could mean receiving almost £54 a week less than retiring one day after.”

In practice, the picture is more complicated.

How much people get partly depends on how many years of qualifying National Insurance (NI) contributions they made during their working lifetime.

To get the full new state pension, both men and women need 35 years of NI. For the basic state pension, men originally needed 44 years of NI, and women needed 39 years. This was reduced to 30 years for both from 2010.

This makes direct comparisons tricky. But another factor is at play.

Many older people on the basic state pension get their income topped up by additional state pension, either the state earnings-related pension scheme (Serps) or state second pension (S2P).

These are based on earnings so men have typically built up a lot more entitlement, said Andrew Tully, technical services director at Nucleus Financial.

“Men who retired on the basic state pension actually get more on average than those on the new state pension, thanks to Serps and S2P.”

However, women on the basic state pension often get much less, because they raised families rather than worked, and built up less additional state pension.

The new state pension has narrowed that gap. It gives men and women roughly the same amount, but that still leaves older women struggling – and some older men too.

Many women struggle on a single basic state pension after the death of their partner or divorce.

Among single pensioners, some 580,000 women live on the state pension alone, compared to just 180,000 men.

In a further twist, additional state pension only rises by consumer price inflation each year, which means they have gone by just 1.7% today, rather than 4.1%. I recently explained why this means the additional state pension is shrinking in real terms this year.

Pensioners on low incomes may be able to claim the pension credit top-up, which guarantees a minimum income of £11,809.20 a year for singles, and £18,023.20 for couples. Yet hundreds of thousands fail to claim.

Having two different state pensions inevitably produces winners and losers. The biggest losers are single women – and a smaller number of men – living on the basic state pension with no Serps, S2P or company and personal pensions.

The DWP says that under the new state pension, men and women should get similar amounts by the early 2040s, more than a decade earlier than under the old system. But that's a long way off and many are struggling today.

And the gap will widen, year after year.