Transport for London has pushed back a decision on the preferred route for the Cross River Tram by 15 months to January 2009.
The proposed Cross River Tram would link Euston and Waterloo with branches to Camden Town and King's Cross in the north, and Brixton and Peckham in the south.
Publication of a preferred route has been scheduled for September 2007, but the latest Transport for London board papers now give a date of January 2009.
Last September TfL published the outcome of the consultation process held at the end of 2006 which asked interested parties to comment on a number of route options.
Last month Mayor of London Ken Livingstone reiterated his commitment to the tram scheme in a written answer to the London Assembly.
"Ultimately I would like to see the tram built both north and south of the river and I welcome the support from the boroughs and many other stakeholders," said the Mayor.
"It is my intention that the Cross River Tram should be built in two phases with the southern part the first to be built. This is in order to avoid the delays that would be involved should the entire project progress at the same time. Nonetheless surveying work is taking place along the whole of the possible route.
"I am fully committed to delivering the full scheme and will lobby Government to obtain the necessary funding to take this forward."
Meanwhile the Liberal Democrat candidate for the Lambeth & Southwark London Assembly seat has criticised Ken Livingstone's transport manifesto for almost ignoring the Cross River Tram.
"The Mayor's Transport Manifesto is a real slap in the face for Lambeth and Southwark," says Cllr Caroline Pidgeon. "Over 14 pages of commitments and just one mention each for the East London Line and the Cross River Tram – it's an absolute joke.
"South East London is the capital's biggest transport black hole, but the Mayor doesn't seem to care – he seems determined to ignore us once again in favour of more investment in North and Central London.
"Residents in Lambeth and Southwark deserve better transport links – such as an extension of the Bakerloo line to Camberwell – and are fed up waiting for Labour to provide them."
Boris Johnson's transport manifesto also fails to mention the Cross River Tram, though Tory London Assembly candidate Shirley Houghton insists that Johnson is "fully committed" to the project.
Liberal Democrat mayoral candidate Brian Paddick mentions trams in his manifesto but without specific reference to the Cross River Tram. He has pledged to publish a detailed proposed tram network soon.
Green candidate Sian Berry also backs the Cross River Tram with the addition of a shuttle tram link along Oxford Street.