Manchester's police commissioner demanded an inquiry into the 'fiasco' of a fake bomb left behind from a training exercise at Old Trafford that forced the abandonment on Sunday of a Premier League soccer match.
The device led to the evacuation of Manchester United's stadium shortly before the scheduled 1400 GMT kickoff of their final league game of the season against Bournemouth.
"This fiasco caused massive inconvenience to supporters who had come from far and wide to watch the match," Police and Crime Commissioner for Greater Manchester Tony Lloyd said.
It also "wasted the time of huge numbers of police officers and the army's bomb squad, and unnecessarily put people in danger," he said in a statement.
Police said the realistic-looking device, which was destroyed in a controlled explosion, had been accidentally left in a toilet by a private firm that was conducting a training exercise.
Two of the Old Trafford stands were evacuated about 20 minutes before kickoff.
The whole 75,000-seater stadium was cleared and the match was called off soon afterwards, the first time in 24 years that a Premier League match had been abandoned on security grounds.
"Whilst this in no way demeans the professionalism of the police and stewards responsible for getting the fans out, or the supporters' calmness and cooperation during the evacuation, it is unacceptable that it happened in the first place," said Lloyd.
Lloyd, who oversees Manchester police but has no operational role, is also the city's interim mayor.
United Executive Vice Chairman Ed Woodward said the club would investigate the incident fully.
The game has been rearranged for Tuesday.
United are almost certain to miss out on qualification for next season's Champions League after local rivals Manchester City drew at Swansea City on Sunday, putting City three points ahead in fourth place and with a vastly superior goal difference.
United are also due to play Crystal Palace in the FA Cup final on Saturday.