The Mayor of London has urged south-east London boroughs to "come to the party" with their ideas for a Bakerloo line extension with a public consultation starting in just a few weeks.
"We're beginning consultation very soon on extending the Bakerloo line beyond Elephant & Castle," Boris Johnson told the London Assembly on Wednesday.
"Where it goes is very much a matter for that consultation.
"We are looking for support from the boroughs that it might arrive in.
"We're looking for interest, we're looking to hear about development potential, about funding packages we can put together with business to support a scheme that has a lot of government interest .
"We really need the boroughs to come to the party and say how they will help us to finance it."
Mr Johnson's comments come in the same week that Southwark Council Peter John was quizzed about the tube plans by a cross-party committee of councillors.
"TfL are going to be starting a public consultation on 29 September on the Bakerloo line extension," said Cllr John.
"My primary argument has always been for Camberwell and Peckham, and the commitment I got from the Mayor a couple of years ago was that he would extend the Bakerloo line in that direction.
"I remain hopeful that that is something that TfL will continue to look at extremely seriously.
"I know it would be of real value to residents of Camberwell and Peckham if the tube ran there."
However, the council leader acknowledged that an extension via the Old Kent Road probably has a stronger financial case: "It's more difficult to see how funding generated from the delivery of the tube to Camberwell and Peckham would deliver the same potential financial gain as you would see running down the Old Kent Road," he said.
"The Old Kent Road is obviously a clear regeneration area and a Mayoral opportunity area where he's said you can have 2,500 new homes.
"Our belief is that you can probably get more housing there while retaining some of the industrial and employment uses that we have there already."
Cllr John added: "I just urge everyone to continue campaigning for both spurs because that's clearly what we need in our borough.
"It can hardly be argued that we would be over-supplied with tube network if we got both of those spurs."