The 84-year-old, who did not want to be named, said he fell hard on the pavement earlier this month after tripping on the metal bar that sticks out the front of the seats.

"I was lying on the ground and a man picked me up," he said.

The man, who was "bleeding freely", was helped to cross the road at the pedestrian lights and taken to the chemist where staff patched him up until he could see his doctor.

He said he needed "a great big bandage" to stop the bleeding.

"Everyone was very nice," he said.

The man had sat down at one of the seats near the pedestrian crossing while he waited to cross the road and ended up tripping on the corner of the metal bar that sticks out.

"I bet I'm not the first person it's happened to," he said. "I lost a lot of skin on my arm. It's a massive graze. I hit the seat and then the pavement. It happened so suddenly. I took my shoe off."

The man went to his doctor who changed the bandage and dressing on his arm, and for consecutive days had to return to have the dressing changed.

He said he wanted to warn others about the dangers of the seat's design, especially for older people. He has written to the council's chief executive officer Peter Schneider about the issue.

"Several of the seats in the city centre have their support brackets back to front, making them perfect booby traps," he wrote to council.

The council has been contacted for comment.