Manchester United have been accused of “bribing” the parents of Federico Macheda and turning football into a “cattle market”. Claudio Lotito, the Lazio president, is outraged at the manner in which he claims the Barclays Premier League champions lured the Italian teenager to Old Trafford.

Macheda announced his arrival in English football on Sunday when the 17-year-old substitute scored a breathtaking stoppage-time winner on his United debut to secure a 3-2 win at home to Aston Villa that returned the club to the top of the table.

But while Sir Alex Ferguson and Cristiano Ronaldo led the tributes to the young striker yesterday, Lotito has called for a change to the rules that prevent Italian clubs from tying a player under the age of 18 to a contract, claiming that United acted unethically when they signed Macheda from Lazio's youth academy in August 2007, the day after his 16th birthday.

United said that they would “not dignify such claims with a response” and there are no suggestions of any rule breaking on their part.

“It is unthinkable and unacceptable that a 15-year-old should be bought as if we were at a cattle market,” Lotito said. “They get the parents on board, giving them handsome compensation, offering them important jobs, which shouldn't happen, because with a 15-year-old it's unthinkable that a club should give millions of euros to his parents, practically buying the parents, and this is a real problem.

“The parents sign on behalf of the players. Normally these are kids who come from not very well-off families and on the back of their economic situation they are incentivised to find alternative economic situations.

“We tried in every way to stop Manchester United from taking our players, but the present Italian regulations don't give you any type of defence. We have to be provided with more reliable and concrete rules than those which govern Italian clubs.”

Macheda will find himself on the substitutes' bench again for the first leg of United's Champions League quarter-final against Porto at Old Trafford this evening. Wayne Rooney, Paul Scholes and Nemanja Vidic, all of whom missed the Villa game through suspension, will return, while Rio Ferdinand, who was absent with a groin strain, could also start, despite the defender sitting out training yesterday.

Ronaldo, 24, joked that Macheda “will listen to the old players, not me”, but, in many respects, the Italian might be wise to do so, even though he has followed a similar path to the Portuguese, who joined United as an 18-year-old from Sporting Lisbon.

Speculation resurfaced over the weekend about Ronaldo's future, with Real Madrid purported to be preparing a world-record £75 million bid, but the Fifa World Player of the Year claimed he was going nowhere. “I'm happy at this club,” Ronaldo said. “I think this is the right club for me.”

Having been asked about Ronaldo's future, Ferguson took umbrage when a similar question was directed at the player, branding the situation as “pathetic”. “How many times have we had that question?” Ferguson said, although he appears convinced that the forward, who is contracted to United until June 2012, will remain at the club. “He will tell you himself that he is at the right club,” Ferguson said. “He knows that. He's settled down and his form is returning and he is looking like he will score all the time.”

United will announce the biggest profits recorded by an English club this week - possibly as early as tomorrow - after the accounts were filed late last week. Pre-tax profits for the year to June 2008 will comfortably eclipse the £59.3 million recorded the previous year.