Street lights could be switched off across Oxfordshire between midnight and 5am in a radical bid to cut carbon emissions and reduce light pollution.

County Hall has been challenged to show it is serious about cutting its carbon footprint by updating outdated street lighting with low-energy lightbulbs - and turning off unnecessary lights altogether.

Oxford city councillor Paul Sargent will todaytable a series of suggestions that, if accepted, would force Oxfordshire County Council - the highways authority - to undertake an audit of every street light, traffic light and illuminated sign.

He wants County Hall to: Undertake an environmental impact study to investigate the possibility of switching off unnecessary lighting between midnight and 5am; Conduct a full audit of civic lighting in their control to ensure lighting is correctly positioned and focused; Investigate the use of energy-efficient light-emitting diode technology as a replacement for sodium and mercury vapour lamps.

And he wants the city council to play its part by: Instructing departments responsible for security lighting on council property, parks, housing and walkways to investigate using LED lighting; Instruct businesses to ensure all non-essential workplace lighting is switched off overnight.

Mr Sargent, who represents the city centre Carfax ward, said: "Light pollution occurs from the use of artificial lighting. In some cases, when light is emitted, it can be seen as prejudicial to health, or a nuisance."

Between them, the county and city councils spent nearly £5m on electricity in 2005-6 for street lights, traffic lights and illuminated signs.

County Hall has set itself a target of switching off the lights in 100 street signs a year, where regulations permit, to save money.

Mr Sargent's motion says: "This council recognises its statutory responsibilities in reducing the nuisance factor of light trespass and takes seriously its moral obligations in raising awareness of light pollution and its increasing impact upon the overall carbon emissions.

"The council acknowledges civic lighting in our public places, parks and highways plays its part in reducing accidents and enabling citizens to go about their lawful business safely.

"However, we also recognise much of our civic lighting stock is ageing, energy-inefficient and in many cases, polluting.

"In fact, most light pollution is caused by ageing and poorly-positioned lighting.

"It's time the city and county councils put their own houses in order."

Thames Valley Police said it would have to undertake crime risk assessments before any lights were switched off.

Police spokesman Toby Shergold added: "We're aware of similar schemes at other councils and we're liaising with Oxfordshire County Council on the possibility of future schemes here, although there are no current plans to reduce lighting."