Formula One's governing body opened an investigation on Monday into McLaren's one-two win in the Monaco Grand Prix amid a controversy over so-called 'team orders'.

The International Automobile Federation (FIA) said in a statement that it was looking into incidents involving the Mercedes-powered team "in light of a possible breach of the International Sporting Code.

"The relevant evidence is under review and a further announcement will be made in due course," it added.

Double world champion Fernando Alonso won Sunday's showcase race, for the second year in a row, ahead of British rookie team mate Lewis Hamilton. The two are now level on 38 points but Spaniard Alonso leads the championship on race wins.

Hamilton revealed afterwards that he had been told to ease off rather than put pressure on his team mate and possibly jeopardise the one-two.

Team orders, effectively manipulating the outcome of a race, have been banned in Formula One since the 2002 Austrian Grand Prix where Ferrari ordered Brazilian Rubens Barrichello to let Michael Schumacher win.

However, McLaren team boss Ron Dennis denied any such manipulation on Sunday.

"We don't have team orders, we had a strategy to win this race," he said.

"I make no excuses for instructing the racing drivers to slow their pace after the first stop and to effect our strategy."

A FIA spokesman declined to say what possible sanction might be faced by the team, who lead Ferrari by 20 points in the championship after winning two of the season's five races so far