Days after the rise in base rates, just 17 out of 150 providers have passed on improved returns to their savers.
The Bank of England recently raised rates by 0.25% to 0.5%, the first rise in a decade.
Many banks are still considering whether to pass on the benefits.
But even if their provider does choose to increase rates in full, some savers will still find themselves worse off than when rates were last at 0.5%.
NS&I is among the providers that have announced an increase. The returns on all its variable rate products, including premium bonds, will rise by 0.25% from 1 December.
However Virgin Money cut savings rates on one of its ISAs on the same day that the Bank of England was raising rates.
Those with Virgin’s ISA Saver saw rates reduced to 0.75%.
That compares to an interest rate of 1.3% when base rates were last at 0.5% in August 2016, leaving savers worse off.
Another Virgin ISA, the Defined Access E- ISA, now pays just 0.51%, compared to 1.56% last August.
Nationwide has promised to pass on the 0.25% rise to all savers whose rates were cut by 0.25% in 2016.
Nevertheless, customers who had a Flexclusive ISA Issue 10 will now expect to get a 1% return, compared to 1.5% last year.
Santander has announced that it will not raise the 1.5% credit savings rate on its popular 123 account.
It will raise rates on some of its savings products from 4 December, but most adults will not see the 0.25% passed on in full.