Irish investors Mr John Magnier and Mr JP McManus yesterday raised their stake in Manchester United, further strengthening their hand in dealing with the club's management.

Further talks are now expected between representatives of the duo and the club, which could result in a number of their representatives being appointed to its board.

The duo's investment vehicle Cubic Expression bought eight million United shares at a cost of #20 million sterling (?29.47 million) from Dutch media tycoon Mr John de Mol to take their total holding to 28.89 per cent from 25.49 per cent.

The further purchase takes them near the threshold that would trigger a full-blown takeover. British market regulations dictate that a full offer for a company must be made when a shareholding hits 30 per cent.

However, sources said the move was aimed at signalling their commitment to the English champions and did not presage a full takeover bid.

In recent weeks the intentions of Mr Magnier and Mr McManus have been questioned by the club's supporters, some of whom have gone so far as to disrupt a horse racing meeting in England.

However, the pair were said to be keen to ensure Manchester United continued to enjoy success on the pitch as well as in the boardroom.

Sources declined to be drawn on whether they would consider a takeover, but making a bid is not believed to be part of their plan. At yesterday's price, the club is valued at around #692 million.

Cubic has pressed United on a number of concerns relating to corporate governance, regulatory compliance, player transfers and the fees paid to transfer agents, and is studying a reply from the club's board to a letter sent in January.

It has not ruled out calling an emergency shareholder meeting or complaining directly to British regulatory authorities if it deems United's response inadequate.

Pressure from Cubic has already prompted the club to have an internal review of its finances and its transfer dealings, and to curb the length of the new contract for club manager Sir Alex Ferguson.

However, sources say that following a frosty period, the relationship between the two sides has improved recently and that Mr Magnier and Mr McManus believe that their concerns are now being taken more seriously. Informal contacts have taken place over recent days and these are expected to intensify in the days ahead.

These may result in the duo seeking board representation, to further underpin their influence at the club. If this happens they would be expected to seek a board representation commensurate with their shareholding level, likely to involve the appointment of between two to four representatives put forward by them, depending on agreement on the size of a reformed board. Mr Magnier and Mr McManus are not thought likely to take up the seats themselves, instead nominating representatives.

Encouraged by the United board's response to their concerns Mr Magnier and Mr McManus have no immediate plans to request the appointment of a new chairman or chief executive, positions currently held by Sir Roy Gardner and Mr David Gill.

Their relationship with the board has been fraught since the public airing of correspondence in which Mr Magnier and Mr McManus criticised the club's corporate governance.

But while they remain keen to push changes, their stance has softened after contact with Mr Gill.

After selling the eight million shares yesterday to Mr Magnier and Mr McManus' Cubic Expression vehicle, Mr de Mol sold three million to an unidentified buyer.

Manchester United could not confirm who bought the shares.

However, the buyer is thought to be Mr Malcolm Glazer, owner of the Tampa Bay Buccaneers and an existing Manchester United shareholder.