Retail chain Toys R Us will deliver an Xbox One for £383 if customers take advantage of a new coupon offer, representing a saving of £45.
And Sony's PS4 UK price is cut to £311 (a saving of nearly £40) if the same trick is applied.
Games deals blog Savvy Gamer has discovered that customers can receive a 10 per cent discount on their next purchase if they buy certain items.
One of the cheapest qualifying items is a plastic Xia Xia Shell, worth £1.
Following the purchase of this, the 10 per cent discount can be applied to either the Xbox One or PS4. Toys R Us is retailing Microsoft's next-gen system at £420, which is already about £10 below the UK RRP, while it is selling the PS4 for the £339, also £10 less than the announced RRP.
The additional discount deal brings the Xbox One price down to £384 delivered (plus £1 for the Xia Xia Shell), and the PS4 price to £312.
Terms and conditions on the ten per cent discount, which are available here, do not state that an Xbox One or PS4 is exempt from the offer.
However, it is not clear if Toys R Us is willing to keep the loophole open.
Customers have until July 31 to buy an item that activates the coupon, and the 10 per cent discount can only be redeemed in August.