The UK’s information security watchdog, the Information Commission, has warned online shoppers against letting retailers share their details with other firms.
Customers of several online companies have complained that they did not realise they were agreeing to join discount services when clicking on links.
They uncovered it when amounts of up to £99 were taken from their accounts.
The companies involved denied being unclear and said customers who had complained were refunded.
One listener told the BBC’s Money Box radio programme that she bought some storage bags from a website selling them.
A month later the company called to see whether she was happy and then asked if she wanted a holiday discount brochure.
“I noticed it referred to a 30-day free trial but then next thing I knew a firm called Break4Free had taken £99 out of my current account without my authority,” the listener told the programme.
“I wasn’t aware that debit card details had been passed on by the original supplier.”
She questioned the transaction but when she asked for a tape of the phone conversation was told it had been deleted. She was refunded in full.
Another listener told Money Box that he had bought a ticket on thetrainline.com and then was asked to click a link to get a £15 discount off his next purchase.
He then re-entered his card details, believing this was necessary to receive the discount.
But he was surprised to find money was then taken from his account by a company called Shopper Discounts and Rewards; he argued that this was not made clear enough at the time of purchase: “Having seen the website again it states there is a £10-a-month charge.
“But a lot of people might not realise and might not check their account to notice the £10 a month charge.”
Deputy Information Commissioner David Smith warned companies that they did not just have to comply with the letter of the law.
“Some businesses (think) so long as it is there in the small print somewhere that’s good enough. But it isn’t.
“It is not about complying with the law it’s about making sure your customers know what’s happening with their information.
“These notices have to be upfront and obvious and if there is financial information and a charge involved you’d expect it to be up there in flashing lights.”
But he warned that customers had to be smart when shopping online too.
“The responsibility isn’t all one way. Consumers shouldn’t go to websites with their eyes shut or blinkers on.”