Manchester United have confirmed that the agent Jorge Mendes acted for Bebé when Sir Alex Ferguson signed the 20-year-old striker from the Portuguese first division club Vitória de Guimarães in the summer's most extraordinary transfer deal.

Bebé's previous agent, Gonçalo Reis, who had represented Bebé when he moved to Vitória just weeks earlier from the third division club Estrela da Amadora, has previously complained he was cut out of the deal before Bebé signed for United. Bebé, included in United's senior squad for the first time tonight, away at Scunthorpe United in the Carling Cup, had not played a single competitive match for Vitória, and Ferguson had not seen him play, when United's manager signed him for £7.4m.

It was known at the time that Mendes, the agent of Ferguson's former assistant and Portugal's then coach, Carlos Queiroz, and a string of Portuguese stars including Cristiano Ronaldo, had acted in the deal, but not that he was Bebé's own agent. A spokesman for United has now clarified that Mendes did act for Bebé in the transfer. "Jorge Mendes is Bebé's agent," the spokesman said. He added that United did not employ an agent themselves on the deal. "We dealt with Bebé's representative and the club."

Mendes's involvement as Bebé's agent raises the possibility that Reis could formally complain to Fifa that Bebé was "poached" from him, which, if proven, would be a breach of the worldwide regulations governing the conduct of agents. Reis would not comment on that, or on the revelation that Mendes acted for Bebé personally in the move.

Fifa's regulations require players and agents to have written contracts with each other, for a maximum of two years. Article 22 of the Fifa regulations prohibits an agent from contacting a player while he has "an exclusive representation contract" with another agent. That is considered to be poaching. A player can, as Bebé apparently did, terminate a contract early, but must have a valid legal reason for doing so or the agent can claim for lost business. Reis said at the time that he had a written contract to represent Bebé as his agent, which had some time left to run. Bebé did write to Reis to terminate that contract, but Reis said he received Bebé's letter on 13 August, two days after Bebé had already signed for United.

Mendes had put the news of Bebé's move, together with a picture of the two of them together, on the website of his agency, Gestifute, and Emilio Macedo, president of Vitória, was quoted formally thanking Mendes for his help, saying Mendes: "Brings money into the country like an export."

Ferguson later revealed that he had never seen Bebé play, in person or on video, before asking the club's chief executive, David Gill, to spend £7.4m signing him, the first time in Ferguson's 36 years as a manager that he has not watched a player he has signed. Bebé had played only pre-season matches for Vitória after moving from Estrela this summer, and Ferguson said Queiroz, at the time still Portugal's coach, had recommended that United sign the forward, a judgment supported by United's scouts in the country.

The fee United paid, £7.4m, was reported to be the buyout clause, €9m, which Vitória had inserted into a new, improved contract with Bebé signed shortly after he joined. Reis had brought Bebé to Vitória originally, and negotiated his first deal, said to be on a smaller wage with a more modest buyout clause. It is not known if Reis was involved in negotiating the enhanced, second deal at Vitória but Bebé moved to United very quickly after that improved contract was signed, and Reis then complained he was cut out of the deal.

Mendes has not said when he first discussed with Bebé the possibility of representing him and his Gestifute agency did not reply to a series of questions about the Bebé deal, although they have previously denied any wrongdoing.