French billionaire Patrick Drahi has increased his holding in BT to almost 25pc in a move that puts the tycoon on the verge of a blocking stake in the British telecoms giant.

The investment vehicle controlled by Mr Drahi, Altice UK, has increased its stake from 18pc to 24.5pc after buying a further 650m shares in the company.

Altice said it did not intend to make a takeover offer for BT, while a spokesman said the group was supportive of the group’s management and strategy.

However, the increase takes the tycoon just shy of a blocking stake that would allow him to oppose resolutions at the company’s annual general meeting and obstruct any rival bidder.

Under UK takeover rules, Mr Drahi does not have to table a bid until he owns 30pc of BT. However, insiders have expressed concerns about his “creeping control”.

Altice UK said Drahi was not seeking a seat on BT’s board, adding that it “continues to hold management in high regard and remains fully supportive of their strategy”.

The stake-building also risks rekindling national security concerns after Mr Drahi’s previous investments triggered a government review.

The Franco-Israeli billionaire first took a 12pc stake in BT in 2021, before increasing it to 18pc later that year.

Then-Business Secretary Kwasi Kwarteng announced a national security assessment amid concerns Britain’s biggest broadband builder could fall into private foreign ownership.

In August last year, Mr Kwarteng said the Government would take no further action.