Fresh questions have been asked about why the lights are on at Norfolk County Council's headquarters in the mornings and evenings.
The Conservative-controlled council has a target date of 2030 to achieve net zero carbon emissions - but political opponents have questioned what sort of message it sends when there are so many lights on in its Martineau Lane building.
Brian Watkins, leader of the Liberal Democrat group raised the issue at a recent council meeting.
He said: "The perception is, from the public, when they walk past County Hall at night is of the lights being left on.
"That doesn't send out a very good message to the public that the council is really serious about putting its own house in order and leading by example on climate change."
But the council, as it has explained before, says it is using low energy LED lighting, with motion sensors triggered by cleaners and security staff.
A county council spokesperson said: "These sensors are triggered early in the morning when the cleaning team starts at 6am, and when the security team do their regular rounds of the building at all hours, including during the night.
“We have programmed the lights to minimise the time they remain ‘switched on’ and also looked at the frequency and timing of security patrols. However we do have to consider the safety and comfort of those using the building."
They said since the major refurbishment of County Hall, which has cost more than £70m, electricity usage has dropped by 20pc and gas usage by 40pc.
Since the coronavirus pandemic began, the majority of county council staff have been working from home.
Conservative Greg Peck, the council's cabinet member for commercial services and asset management, said: "It is extremely disappointing that the Liberal Democrats are fixated about the timing of low energy use LED lights at County Hall for staff who are working in the evenings.
"It is this administration that is actually tackling carbon emissions and is focused on addressing climate change.
"Since the Conservatives took over in 2017 we have reduced the carbon footprint of our built estate by 68pc and we’ve reduced carbon emissions from water consumption by 52pc.”
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