The move has perplexed the giant builders merchant which took full control of the trade and DIY supplies specialist last month.
Travis Perkins said: “Travis Perkins has been informed by the Office of Fair Trading that it intends to review Travis Perkins’ recent acquisition of the remaining 70% of Toolstation.
“While Travis Perkins will cooperate fully with any review, the Company sees absolutely no basis for this notification and will be seeking clarification from the OFT at the earliest opportunity.”
Travis Perkins bought a 30% stake in the business for £18m in 2008 before securing the rest of the company last month.
Toolstation has 103 outlets and a strong online presence.