Christopher Heaton, from St Helens, was working on the Leftbank riverside apartments in Manchester city centre - part of the Spinningfields development - when he was dragged over the guardrail on a scaffolding platform after becoming entangled in a chain.
Liverpool Crown Court heard the 25-year-old suffered fatal injuries after falling approximately seven storeys on 29 April 2004. Another worker, who does not want to be named, was also injured and the incident has had a long-term psychological impact on him.
The court was told Mr Heaton had been using a chain from a scaffolding platform to adjust a steel beam three stories above him, when one of the supporting brackets gave way. He was struck by a falling steel block, became entangled in the operating chain, and was dragged over the edge of the scaffolding.
An HSE investigation into the incident found that the wrong studs had been used to secure the chain, and that the work had not been properly planned or monitored.
Amec was found guilty of breaching Section 3(1) of the Health and Safety etc Act 1974, by failing to ensure the safety of workers, following a trial at Liverpool Crown Court. The company was fined £300,000 and ordered to pay £333,866 towards the cost of the prosecution on 29 June 2012.
Shawton Engineering pleaded guilty to breaching Section 2(2)(a) of the same Act by failing to provide and maintain a safe system of work. The Merseyside company, which has gone into administration, received a nominal fine of £1,000 with no costs.
Neil Jamieson, HSE Principal Inspector for Construction, added: "It is horrifying that Christopher Heaton was dragged off a scaffolding platform more than 20 metres high, causing him to plummet to his death.
"This was a major construction site, and the work taking place there should have been properly planned and managed.
"If either Chris's employer, Shawton Engineering, or the principal contractor on the site, Amec, had acted differently then his life could have been saved."