Currys PC World today apologised for forcing customers to pay an extra £40 for pre-configuration on their laptops that they didn't request – a dodgy practice brought to light by consumer charity Which?

Since 2015 more than a hundred customers have complained to Which? about the aggressive sales tactic.

Despite ordering online or going to a store after seeing an advertised price, customers were told that only laptops already loaded with an operating system, etc remained in the shop, which meant they had to pay more.

One punter was ordered to pay an extra £40 or she'd be sold a blank laptop, Which? said. When another refused to cough and drop the extra cash, the staff member said they would have to charge them £20 for the USB stick.

A grovelling spokesperson for Currys PC World said it was sorry for being rumbled the sales approach: "We are sorry to hear that some customers have been charged for a Knowhow Laptop Set-up service on their new machine when they did not request it.

"While setting up machines in advance enables customers who want the service to benefit from it straight away, it is not something everyone needs.

"We are urgently re-briefing our stores now to remind them that, in the small number of cases where only pre-set-up models are available, customers should not be charged for the service when they buy their laptop."

Currys PC World advised affected customers to contact whichsupport@dixonscarphone.com.

Which? said the types of complaints it received suggested a breach of the Consumer Protection from Unfair Trading Regulations under "bait advertising".

There are 31 practices listed as being unfair under the regulation, which state a retailer cannot lure a customer into their stores with special prices if they know they won't be able to honour them.

Currys PC World owner Dixons Carphone reported plunging profits in the six months to December, down to £61m, compared to £154m in the prior year. The drop was chalked up to UK customers skipping mobile upgrades – a move it warned that could trigger further closures across its stores.

Electronics retailing on the high street isn't a great place to be these days: last month PwC failed to find a buyer for gadget emporium Maplin.

That followed the removal of its trade indemnity, as exclusively revealed by El Reg last autumn, due to worries about its overheads coupled with high debt, and the fact it was losing sales to online giants including Amazon. ®