The borough's bosses believe that the vast £1.5 billion scheme will produce no more carbon emissions than the existing schemes on the site, despite quadrupling the number of homes.
The council has produced figures that show that a 'normal' scheme of this size would double the amount of greenhouse gasses produced.
But the local leaders announced yesterday that they were determined to ensure that the 69ha scheme would make a contribution to 'hitting the UK's Kyoto obligations'.
Southwark leader Nicholas Stanton said the area - which London mayor Ken Livingstone has recenrtly declared an Energy Action Area - should push the environmental agenda.
'Growth on the grand scale required at Elephant and Castle has environmental implications that call for responsible planning right from the outset - otherwise it's almost criminal,' he said.
'We will increase the size of Elephant and Castle by 270 per cent without any increase of carbon emissions beyond their present levels.
'This is not a pilot, this is not a gesture - we have the opportunity to set the standard for the rest of the UK to follow,' he insisted.