London - Spain claimed Olympic hockey officials caved under pressure from their British opponents on Tuesday as the hosts reached the semi-finals for the first time since 1988.
The game, which finished 1-1, saw a succession of late corners forced by 2008 runners-up Spain overturned by the umpire.
When the final whistle sounded, some Spanish players converged on the South African umpire John Wright, who had been officiating at the end they were attacking.
Spanish officials then came on to shepherd their players away. Spain finished third in Pool A and are out of the competition.
A furious Daniel Martin, coach of the Spanish team, told reporters that the International Hockey Federation (FIH) would have to look into the conduct of their officials.
"It cannot happen that an official changes his decision twice because he is surrounded by opposition (British) players," Martin told a crowded press conference.
"We are in a tournament with clear favourites and these countries are being favoured.
But British coach Jason Lee defended his players, insisting they were correct to protest the corners.
"I don't know that there is any favouritism, but what is clear is that in hockey we have lost 50/50 decisions and it is difficult for an umpire to make decisions under pressure situations," he said.
"When we are talking about progressing into the medal rounds that pressure becomes even more significant. It is not life or death, but it is really important and that is why the reactions are coming as they are."
British captain Barry Middleton added: "I know we don't want to surround the umpires, but we have worked so hard for this moment and to have it taken away for something that is not right, then the emotion comes through."