Newcastle chairman Freddy Shepherd is expected to resist any takeover bid by the Jersey-based Belgravia Group.
A statement released to the Stock Exchange this morning confirmed that Belgravia are investigating the possibility of launching a bid for the club.
It is understood they are in talks with former chairman Sir John Hall over his 28.8% stake, while his son Douglas, Shepherd's deputy, controls a further 12 per cent.
However, the feeling on Tyneside is that Shepherd, who has increased his stake to almost 28% in recent years, will scupper any plans for a takeover should the potential purchasers secure the Hall family's holding.
Stock Exchange rules mean the acquisition of a 30% share of the club, which has a current market value of around £81million, would trigger a formal takeover bid, although it would then be up to the remaining shareholders to decide whether or not to accept.
Shepherd, who has shown little sign of wanting to take Newcastle back into private ownership, seems unlikely to sell up.
Sir John revealed in June that he had received 'expressions of interest' in his shares, and speculation named US hedge fund Polygon as one of the interested parties at the time.
Newcastle plc were adding little to the debate today, saying only: 'The club's position remains the same as it was in June when we were first informed that Sir John Hall was in talks with other parties.
'We communicated our position to the market in June and we have nothing further to add.'
Belgravia's statement came after speculation at the weekend that it could formalise its interest in Newcastle.
It said: 'Following recent press speculation, The Belgravia Group ('Belgravia') confirms that it is examining the potential opportunity of acquiring Newcastle United plc... which may or may not lead to an offer for the Company being made by Belgravia.
'A further statement will be made if appropriate.'
However, a spokesman for the group insisted that the discussions are at a 'very preliminary' stage and that any offer is a long way off.
He said: 'It is at a very, very early stage. In terms of a timetable, it is far too early to say.'
The news caused a buzz on Tyneside amid suggestions that a successful bid would lead to millions being ploughed into the team.
Mark Jensen, editor of fanzine The Mag, said: 'The club certainly is not in the greatest state it has ever been in when you look back to the Bobby Robson era in its pomp and we were competing in the Champions League.
'It is maybe not a case of apportioning blame, but when you look at the current squad, it's a bit thin on the ground.
'We can maybe put out a decent first XI if we get a striker in, but we have got to move forward now, and if a new investor can help that, then that can only be good.'
Belgravia Group is a private company which has diverse interests including construction, hospitality, aviation and sports marketing.
Today's news had a positive effect on the club's share price, which rose nine pence to 70p within two hours of the announcement.
Commentators have predicted at offer of between 10% and 15% above the market value of the shares, which would see the Hall family rake in between £35m and £40m.
Sir John, who made around £70million from the sale of the MetroCentre, bankrolled the club's return to prominence after completing his own takeover during the early 1990s.