BT has said it is both "disappointed" and "surprised" by speculation it might be split in two by the telecoms regulator Ofcom.
Would callers enjoy cheaper calls?
The company was responding to a report in the Financial Times that said Ofcom was considering breaking up BT, which still has 70% of the fixed-line market.
While BT is against such a move, a number of its competitors have long called for such action.
Ofcom said any changes to the sector were "hypothetical" at this stage.
The regulator is publishing the initial findings of a wide-ranging review of the telecoms industry on Wednesday.
According to the report in the Financial Times, BT's network infrastructure could be split from its retail arm.
Those in favour of the complete separation of BT Wholesale from BT Retail say it would reduce regulation, and give rival companies easier access to customers, resulting in wider choice and cheaper phone bills.
Their claim is that BT Retail currently gets an unfair advantage, something BT denies.
"We are disappointed and in other ways we are surprised because it has been looked at before and has not convinced people this is a sensible way forward," said a BT spokesman.
Ofcom said its strategic review of the telecoms sector "will examine all the major questions emerging from the sector in the future".
It added: "However, we will not draw any conclusions from the review until we have more evidence from research and the views of all stakeholders until later in the year."
Telecoms expert Christian Maher said splitting BT could be a good thing for consumers, leading to more aggressive cost-cutting.