The Cross River Tram may initially be built only south of the Thames due to opposition from Camden Council, Ken Livingstone has revealed.
Responding to a question from Lambeth and Southwark's London Assembly member Val Shawcross at Mayor's Question Time in City Hall on Wednesday, Mr Livingstone revealed that he had instructed officers to investigate the possibility of building the southern tram routes from Peckham and Brixton first and terminating them south of the river.
The northern sections from Waterloo to Euston, King's Cross and Camden Town could then follow at a later date.
Green Party London Assembly member Jenny Jones welcomed the Mayor's proposal to build the Southwark and Lambeth parts of the tram route: "I'm thrilled that he's going to go ahead with it anyway," she told the London SE1 website.
"South of the river there's consensus ... that it's the right thing to do."
Jones believes that a possible Lambeth and Southwark tram would quickly prove itself as a quick and efficient means of transport and win over its north London detractors. "I think it will go ahead in North London. There's no doubt about that."
Both Southwark and Lambeth councils have backed the Cross River Tram proposals, but local authorities north of the Thames have been lukewarm.
Val Shawcross told the London SE1 website that she was especially pleased that the Mayor had opened up the prospect of moving the Cross River Tram up his list of priorities – ahead of the West London Tram scheme which has met fierce resistance from councils. "Their loss is our gain," she said.
Southwark's executive member for regeneration, Cllr Richard Thomas, said: "Southwark certainly supports any approach which puts the borough at the top of the priorities list, and it would be great to see things moving more quickly. This initiative is to be welcomed if it means bringing our part of the tram to fruition earlier, and before the Olympics.
"We are continuing to press the Mayor of London and the Government to provide the funding to make this happen, because this is our best chance in decades to get Southwark well and truly on the public transport map."
In February Camden Council leader Cllr Keith Moffitt (Lib Dem) said: "We are extremely concerned that the proposed tram will cause local traffic congestion and safety problems for local people in residential streets."
In late 2006 and early 2007 a consultation on the route options was carried out. Key questions include whether the Peckham and Brixton branches should divide outside The Old Vic theatre or at Elephant & Castle.
The results of that consultation process are expected to be announced shortly.
Whether any part of the Cross River Tram will be built depends on the availability of funding and the Mayor says that he will continue to make the case for the tram to central government.
"These are long-term schemes and you need to keep your eye on the prize," says Shawcross, who as a former leader of Croydon Council well remembers the 15-year campaign to bring Tramlink to that borough.
"You stay on the case arguing for the money and eventually you get it."
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