(Adds detail, Barclays comment)
LONDON, Dec 1 (Reuters) - Britain's Payment Systems Regulator (PSR) has fined Britain's Barclays bank 8.4 million pounds ($10.2 million) for failing to give retailers full information about card costs, the watchdog said on Thursday.
Over three years from December 2015 retailers were unable to easily understand the transaction fees associated with accepting certain types of card payments, making it harder to compare prices in search of better deals, the PSR said.
Card fees paid by retailers are passed on to consumers in the form of higher prices.
"It's vital that retailers and consumers get value for money on payment services – the interchange fee rules are an important part of making sure this happens," PSR Managing Director Chris Hemsley said in a statement.
"Barclays’ failure to be transparent with retailers about the fees they pay for card services meant retailers could have been missing out on better deals."
The failure came to light during regular monitoring activity, the PSR said.
A Barclays spokesperson said it had reached a resolution with the PSR after an investigation into its historic compliance with interchange rules.
"As part of this resolution, Barclays has agreed to pay a penalty of 8.4 million pounds," the bank said, adding that it had co-operated fully with the PSR investigation.
The PSR fined NatWest bank 1.8 million pounds in May for overcharging interchange fees on credit cards. ($1 = 0.8234 pounds) (Reporting by Huw Jones and Lawrence White, Editing by David Goodman)