The new Greater London Authority headquarters building designed by Foster and Partners and engineered by Arup has been hit by a row over its energy consumption.
The argument centres on lighting which, the GLA claims, will guzzle far more power than originally promised by the designers, undermining the building's status as an environmental showpiece.
Assertions that the 45m high glass-clad structure will use just a quarter of the power consumed by typical high-specification office blocks are doubtful, said the authority. In fact, electricity consumption will be no better than an average office building.
Environmental committee chair Samantha Heath revealed that the consumption target of 8 watts per m 2had been missed by a wide mark.
A review will now take place to determine the building's true environmental performance, she said. 'We now know lighting will use 11 watts per m which is no better than many of London's office buildings and is not a very ambitious target, ' said Heath, a civil engineer. 'There are statements and then there is actually living the dream. The GLA must know what it is letting itself in for.'
But Arup and Fosters insist that the GLA has got its figures wrong, and said there is no uncertainty hanging over energy efficiency.
'Eight watts is news to us and has never been discussed with the design team. It's frustrating having these figures plucked out of the air, but you are dealing with a political organisation so we must take the bruisings, ' said Arup associate director James Thonger.
'When all lighting is considered, such as decorative lighting, the chamber, plant rooms, exhibition space, committee rooms, then we do get a figure higher than the optimum target quoted by the GLA committee. But it really comes down to what is taken into account.What we have achieved is still energy-conscious, ' he said.
Foster and Partners admits that power consumption will be closer to 11 watts per m 2- but only when all the lights are on. 'At normal usage consumption is expected to fall well below this figure, ' said a spokeswoman for the practice.
Solar panels are now being reconsidered by Fosters and the GLA as one way of ensuring the assembly building remains environmentally sound. However, the authority must first go cap in hand to the government to raise extra funding.
Furthermore, installing solar panels retrospectively may disrupt the tight construction timetable.
Heath has also heaped further embarrassment on Fosters by revealing that the new building is too small to house all key departments, forcing some, such as the Metropolitan Police Authority, to be based in 'overspill' offices.
The revelation also weakens London mayor Ken Livingstone's dream of forcing all GLA staff to use public transport when getting to and from work. Heath fears the overspill departments could be banished to areas poorly served by public transport, giving staff no option but to take the car.
She said: 'Even though the GLA is a lean organisation, the building is not large enough for the assembly and its functions. It's a great shame this has not been thought through.'