The grocery giant is offering toys at half price online and in-store, including many of the lines included on yesterday's Dream Toys list.
Mattel's Jet Pack Buzz Lightyear is available in-store for £19.99, compared with the recommended retail price of £39.99.
The Kidizoom VideoCam, from VTech, will be selling at £29.99, down from an official price of £59.99.
The biggest saving is on Hornby's Thomas The Tank Engine train set which normally retails for £139.99 and will be £69.99 from today for a week.
Grant described the Sainsbury’s price cuts as "stupidity" and added: "These price reductions are taking the figure below the trade price. Sainsbury’s will be making a loss on every single one of these toys they sell.
"They are hoping to drag people in to the shops and make up any loss through sales of food and petrol."