Money spent on street lighting in Preston has been almost halved in a year.
The Royal Society for the Prevention of Accidents has urged councils to be cautious about dimming or switching off street lights, warning that poorly lit roads can increase the risk of car crashes.
Between April and December 2018, Preston City Council spent £16,000 on street lights , according to financial data from the Ministry of Housing, Communities and Local Government.
During the same period in 2017, the council spent £30,000, after the figures were adjusted for inflation. That's a real-terms cut of 47 per cent over one year.
Across England, spending has fallen slightly, and many local authorities have slashed their budgets by 50 per cent or more.
Money saved by switching off street lights can come at the cost of personal safety, the Royal Society said.
It added that the risk of driving or walking in darkness "may ultimately lead to lives being lost" if councils are not careful.
Head of road safety, Nick Lloyd, said: "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, and accident rates should be monitored.
“It is also important that councils do all they can to warn drivers, riders and walkers that lights are being switched off or dimmed, and give advice about what they should do to protect themselves.”
But, the Local Government Association argued that reducing street lights and investing in dimming LEDs can lower energy costs in the long term.
An LGA spokesman said: "This saves taxpayer money, while improving the environment in a safe way. With local government facing a funding gap of £8bn by 2025, reducing or dimming street lights can also free up vital cash to protect under pressure services such as child protection, adult social care, collecting bins and filling potholes.”
An MHCLG spokeswoman said: “It is for each local highway authority to decide what level of service they wish their street lighting network to deliver."