Birmingham's Bullring shopping centre said it stopped a major 'flash mob' exercise involving dozens of people.
The Bullring was packed with shoppers on Saturday
But members of the group said the event, in which people froze for five minutes, took place and images went on the social networking website Facebook.
The Bullring said it prevented a "major blockage". A spokesman added that the shopping centre "could not afford customers not being able to get past".
A spokesman for the 'flash mob' said they had not intended to annoy people.
He said members of the group had gone in and "dispersed as individuals" across the area.
The spokesman said: "When it reached the time that had been agreed, everybody froze. Security told us to move but we all remained frozen."
John Kuzminski, who has been involved with the group since the beginning of this idea, said those taking part were "harmless".
He said: "Our intentions were not to disrupt or stop trading in the Bullring."
The Bullring's general manager, Tim Walley, said on Saturday lunchtime that security had spoken to a group which had assembled outside and was told they would reconvene in smaller groups in the shopping centre.
He said: "We saw one of them with a loud-hailer.
"We couldn't afford customers not being able to get past. We'll be looking at 180,000 people coming to shop on a Saturday."
A flash mob is a large group of people who assemble suddenly in a public place, perform an unusual action for a brief period of time, then quickly disperse.