The British telecoms giant is only the tenth firm to experience public criticism from the panel since 1967 after investment bank Rothschild failed to ensure that the company complied with the Takeover Panel's code of practice.
The Takeover Panel issued a "statement of criticism" over the purchase of more than 30 per cent of the shares in specialist broadband provider PlusNet by BT in November 2006.
According to the Times newspaper, BT is conducting a review of fees paid to the bank and is taking legal advice on the matter. The Takeover Panel is urging the company to reduce its stake in PlusNet to below 30 per cent.
The purchase violates Rule Nine of the Takeover Code, which states that any company purchasing more than 30 per cent of the shares in a business must make an offer to all shareholders, and Rule Seven, which governs changes made to an offer document.
Rothschild is understood to have breached the Takeover Code twice in recent years when advising clients about share purchases