Small firms must ensure they know what members of their workforce are up to on their premises at all times, even during meal brakes, the Health and Safety Executive (HSE) has warned.
The reminder was issued after a coach building company was prosecuted over the death of a 16-year-old apprentice.
Ashley Saunders, who had been playing football on his lunch break, fell to his death when trying to retrieve the ball after it had been kicked on to a roof.
He fell 5.3 metres through a skylight to the concrete floor below and suffered fatal head injuries.
Vincent Joyce, HSE principle inspector, said: "We don't want to stop healthy break-time activities such as football but employers need to be fully aware of what their employees get up to on their premises, and take action to protect them."
SMEs should take particular care with vulnerable employees, he added.
Earlier this month, the HSE stated that there was a slight fall in the number of workplace fatalities in 2007-08 when compared to the previous 12 months.
