The ex-striker was under scrutiny for a potential conflict of interest concerning his son's transfer from NAC Breda.

Sydney van Hooijdonk, the top scorer for NAC, left the club in January to join Portuguese side Estrela da Amadora on a free transfer.

Reports suggest that NAC had previously declined a £433,000 offer from Estrela, with a 10 per cent sell-on clause.

The allegations centred on Pierre, who was employed as a technical adviser at NAC, allegedly intervening in the transfer process to assist his son, rather than serving the club's best interests.

He was accused of passing contact details to the Portuguese club, despite an obligation to remain distanced from negotiations involving his son.

This situation angered NAC supporters and prompted an internal investigation by major shareholder foundation STAK.

The investigation concluded that Pierre van Hooijdonk had not acted improperly.

The club stated that correct procedures had been adhered to, considering the unusual circumstance of a father-son situation.

STAK chairman Martijn Vermeeren said: "That creates clarity and prevents inaccurate perceptions."

He suggested the introduction of a protocol for formally withdrawing from decision-making where conflicts of interest may arise.

The investigation also highlighted issues surrounding information leaks during the dispute, stating: "Both the leaking of information by one of the certificate holders and the public disclosure of private correspondence by an advisor are undesirable and harm the club."

Pierre resigned from his position at NAC in May following the controversy.

Sydney's time in Portugal was short-lived; he scored once in 12 appearances before returning to the Netherlands.

He is now on loan with PEC Zwolle.

NAC were relegated last season and now compete in the Dutch second tier.