Up to three million vulnerable consumers have problems using new chip and pin cards, the National Consumer Council (NCC) has said.
Not everyone finds chip and pin easy to use
Many elderly and disabled consumers struggle to remember and properly key-in their pins, the NCC added.
The group said banks should do more to tell vulnerable customers that non-pin number cards can still be requested.
From 14 February, consumers with a chip and pin card will no longer be able to sign for a purchase.
As a result, vulnerable consumers, that do not know or can not key-in their pin numbers, may have their cards refused in shops.
Easy to use
"A year ago we urged the banks to launch an information campaign and improve bank staff awareness of the chip and pin alternatives," Claire Whyley, deputy director of policy at the NCC, said.
"We are really disappointed that banks haven't taken their responsibilities to vulnerable customers more seriously. Three million people could find themselves high and dry at the checkout," Ms Whyley added.
In response, the Association of Payment Clearing Services (Apacs) said its research indicated that most people with visual impairments and disabilities found chip and pin as easy to use as the old signature system.
"We accept, however, that some disabled cardholders may find using a pin more difficult and we are pleased to see that they are contacting their banks ahead of the change and requesting a chip and signature card so they can continue to sign," Sandra Quinn, Apacs spokeswoman added.
To date 100,000 chip and pin signature cards have been issued, Ms Quinn added.
But this figure is dwarfed by the 127 million standard chip and pin cards currently in circulation in the UK.
Chip and pin cards aim to cut fraud by including a smart chip, which can store more information than the usual magnetic strips, and also by having users verify transactions by keying in a pin number rather than signing a receipt.
Over the past two years card issuers have been busy replacing all credit and debit cards in the UK.