More than 20,000 street lights in Wiltshire could be switched off or dimmed between midnight and 05:30 in an attempt to save money.
The Conservative-led authority said the street lights cost more than £1.2m per year.
So far 1,300 lights have been converted and illuminated bollards have been switched to low energy lights.
Lights at junctions, crossings and high crime areas will be unaffected, Wiltshire Council said.
Leader of the Liberal Democrat opposition, Councillor Jon Hubbard, said his party supported the idea of saving money and reducing carbon emissions.
"At the moment all the debate is whether they are on or off.
"We believe significant savings can be made by switching to efficient LED lighting and we have previously proposed this but it was turned down.
"Much of financial and carbon savings proposed by the council could be achieved this way."
Under the proposal, which is out to public consultation, a "small number" of lights which are no longer required could be turned off permanently.
A Wiltshire Council spokesman said lighting where there are CCTV systems, in town centres, and in areas where crime is a problem will remain on.
"The operation of the scheme will be monitored and changes will be made as necessary in the event of problems.
"Anyone wishing to contribute to the consultation has until 30 September to make their views known," he added.
Earlier this year Swindon Borough Council abandoned a trial which saw 433 of its 26,000 lights switched off.
The trial was supposed to save £20,000 in energy bills - but it will cost £30,000 to reverse the decision.