The Fire Brigades Union called the store a "death trap."
The blaze started in an electrical cable and spread to furniture made of flammable polyurethane foam.
"When crews arrived they found thick smoke billowing from the six-storey building and people screaming for help from the windows," according to the Fire Brigades Union. "Firefighters fought the blaze for two and a half hours while helping people escape by the shop's doors, windows and roof."
"The store had no sprinkler system, so the fire had plenty of time to spread before firefighters arrived," the union said. "There were thick bars on the upper-floor windows that fire crews attempted to pry off with axes and crowbars, but so strong were the bars that they had to wait for specialist cutting machinery. Meanwhile, a vital means of rescue was frustrated."
There were about 500 people inside when the alarm sounded. Among the victims was Woolworth employee Cyril Baldwin, 68, who served as an auxiliary fireman during World War Two and died trying to save others.