The debt-laden media tycoon Patrick Drahi is thought to have quietly sold part of his near-25 per cent ownership of BT in recent months, according to a new analysis that has set tongues wagging in the City.

The French-Israeli billionaire is the FTSE 100 company’s largest shareholder, with a declared stake of 24.5 per cent. But research suggests that Drahi may now directly own as little as 10 per cent of the company, with the rest held on his behalf by banks as borrowed shares.

It comes as Drahi’s Altice group, which holds telecoms assets across the world, faces growing pressure from bondholders. Altice is reported to have racked up debts of $60 billion and is in talks with bondholders over debt restructuring plans. Drahi has sold off several assets to raise cash.

The suggestion of the research into BT is that Drahi has been selling directly-owned shares in the company to raise cash, while ordering bankers to borrow the equivalent number on his behalf to retain his aggregate stake in BT. Borrowing shares like this is commonly used as a cheap way of obtaining an interest in a business.

Analysis by New Street Research — disputed by allies of Drahi — suggests that while the tycoon retains a hold over 24.5 per cent of BT’s voting rights, much of his stake may now be made up of borrowed shares held by banks, Morgan Stanley among them.

This could be good news for BT, whose share price has come under pressure amid concerns Drahi may suddenly need to sell his stake, flooding the market with shares.

In a research note that has pricked ears within the company, the New Street partner James Ratzer wrote: “We have heard people say there is a potential 24.5 per cent overhang on BT’s share price because of Drahi’s holding and potential debt issues he might have, and therefore he could be a forced seller. However, we now believe that this is materially overstated.”

New Street’s research was prompted by figures showing an unusually high proportion — about 17 per cent — of BT’s shares are on loan. New Street believes that between 10 per cent and 14 per cent of this relates to Drahi.

The report speculates that Altice’s shake-up may have been prompted by the need to pay down debt taken on to invest in BT. The FT reported last month that Altice had taken on loans of £1 billion against its stake in BT. Ratzer estimates that Drahi would have raised £980 million in cash since February by exchanging direct shares for borrowed shares.

BT, Altice and Morgan Stanley declined to comment.