Colin Rogers, 59, of Andrews Drive, Langley Mill, trading as Central Demolition & Salvage Specialists, was the principal contractor at the former Jolly Colliers pub on Jessop Street, Ripley, in May 2011.
Southern Derbyshire Magistrates' Court was told that the Health & Safety Executive (HSE) received complaints from three different members of the public, one of whom took photographs of some of the unsafe work taking place at the site. They showed workers on the roof of the two-storey building without any measures to prevent them from falling.
As a result, HSE gave Mr Rogers advice on safe working at height. However, during a follow-up visit to the site on 19 May, inspectors saw unsafe practices still taking place, including one worker throwing timber from the edge of the building at roof level with no safety measures to stop a fall.
Two prohibition notices were served by HSE preventing any further work until a suitable demolition plan was adopted and adequate fall prevention measures introduced.
The court fined Mr Rogers £2,500 and ordered him to pay costs of £2,500 after he admitted breaching Section 3(2) of the Health and Safety at Work etc Act 1974.
Speaking after the hearing HSE inspector Lee Greatorex said: "The dangers that the workers faced were so great and so obvious that no fewer than three members of the public took the trouble to contact HSE with their concerns, one of them with photographs.
"Colin Rogers blatantly ignored HSE's advice leaving a worker at the site exposed to an unnecessary risk of a serious or even fatal injury. Demolition and work at height are high risk activities. There is a need to adequately plan for such work and ensure those plans are fully implemented and monitored effectively to ensure the safety of those involved."