The move follows a meeting with officials at Westminster City Council, one of a number of councils disputing their Census figures, which they argue are inaccurately low and could lead to cuts in Government grants next year.
A spokeswoman for the mayor said: 'We had a very useful and productive meeting and the mayor supports calls for further information being made available regarding the Census.'
Westminster head of communications Alex Aiken said that having Livingstone on board was a significant boost for the campaign: 'He is a high-profile figure who is at the heart of debates on London's future.'
The campaign has a degree of urgency as the Government decides on grant allocations to local authorities in January.
Westminster is currently awaiting a reply from Treasury minister Ruth Kelly who was asked in a letter by the council last week to back an independent review.
The possibility of legal action by the council over the figures is also an option being discussed.
The Office for National Statistics' Census results saw a 26 per cent drop in Westminster's population. The campaign by the council, launched last month, estimates that as many as 64,000 are missing from the figures.
Other councils also lobbying include Norwich and Manchester city councils and Forest Heath district council in Suffolk.