The Football League has been urged by Championship clubs to investigate the influence of Jorge Mendes, the Portuguese agent, at Wolverhampton Wanderers, and a promotion rival plans to write to the authorities.

Mendes, whose clients include Jose Mourinho and Cristiano Ronaldo, has close links with Wolves and there is growing unease among clubs in the division over how far his influence extends.

The Telegraph has seen a draft letter from a rival club, which will be addressed to League chief executive, Shaun Harvey, and the Football Association, outlining those concerns and there is understood to be a growing clamour from others to launch an inquiry.

Leeds United, Aston Villa and Derby County are thought to be three of the teams who have voiced dissatisfaction in the past to the Football League.

Mendes, who has no official title on the Wolves website, has a number of clients at the club, including head coach Nuno Espirito Santo, £15 million midfielder Ruben Neves, attacker Diogo Jota (on loan from Atlético Madrid) and £7m winger Ivan Cavaleiro.

It is alleged that “almost half” of 25 players signed in the past 18 months have been from Mendes’s Gestifute firm, though this has not been officially confirmed.