Ambulance services were alerted and were instructed to divert patients to neighbouring Monklands District General Hospital and Hairmyres Hospital, in East Kilbride.
About half an hour later, neighbouring Monklands Hospital was also hit by power cuts affecting lighting systems in the accident and emergency department.
Save that it is largely free from religious sectarianism, Paisley South is similar to nearby Monklands, where Labour only just held an even safer seat at a by-election in 1994.