Postmen and women in Exeter have expressed fears for their safety as a result of street lights being turned off in parts of the city.
They have taken their worries to Exeter MP Ben Bradshaw, saying they fear a fatal accident could happen in the dark.
Devon County Council's money-saving decision to switch of street lights between midnight and 5.30am affects Alphington, St Thomas, Cowick, Exwick, Duryard and Pennsylvania.
The letter to Mr Bradshaw from Darren Rowbotham, health and safety representative for the CWU's Western Counties Branch,said delivery staff in Exeter have expressed concern about the impact of the street light move.
He wrote: "It means they are now starting their day in complete darkness, which is hazardous enough, but will be much worse in wintry weather.
"Street lighting is there for a reason and as such turning it off or even dimming it could have serious implications.
"We believe the decision to turn off the street lights has lead to an increase in the "fear factor" among our staff and residents of Exeter.
"Street lighting improves safety for our drivers, bicycle riders and pedestrians many of which walk to work in the dark using mobile phone to light the walkway ahead.
"Another fear is now that the weather is changing and getting colder without street lights this journey will be a greater hazard for the delivery staff with black ice, snow, wind and rain all adding to an already hazardous journey?
"A tragic example of these risk becoming a reality is the death of a Bedfordshire student who died having been hit by a taxi last December. At the inquest, the Coroner ruled that a lack of street lighting had materially contributed to his death.
"We feel councils should only reduce lighting if they are sure that it will not lead to an increase in accidents or put personal safety at risk which is something we feel strongly has not happened in Exeter and fear fatal accidents may arise from the darkness.
"While appreciating the difficult task faced by local authorities in dealing with such swingeing cuts to budgets, there must be a balance between reducing expenditure without creating an increased risk to the general public.
"Other councils are investigating the possibility of achieving costs savings by switching to modern LED street lighting. Whilst upgrading the street lighting this will bring in electricity cost savings in the medium to long term."
Ben Bradshaw said: "Devon County Council's Exeter street light switch off has been a disaster from the start. It must now be reviewed. Local councillors and I have been inundated with complaints from residents.
"Now, local postmen and women and Royal Mail management have raised serious safety concerns. They start work in the dark and, if we get wintry weather, will face additional hazard. They are quite right to call on the council to introduce energy saving technology instead. This is what we've called for from the start and the council has still not explained why it won't do it."
