They have hired solicitors and formed the London Public Entertainers' Collective in an attempt to persuade LT to give members licences so they can busk without fear of being moved on or prosecuted.
Yesterday they held their first 'action day'. About 50 members performed in groups of half a dozen or so at 'above ground' busking venues in central london such as Piccadilly Circus, Leicester Square and Gerrard Street.
They collected 500 signatures for a petition which, after more names are added, will be sent to London Underground and have won the support of ex-buskers such as Leo Sayer, who went on into mainstream pop. However, a letter to Gordon Sumner, alias Sting, has not yet received a reply.
London Underground is unmoved. It condemns buskers as a safety hazard, saying they drown out emergency announcements and cause crowds to form in confined spaces. Both the transport authorities and the police believe a licensing scheme would be bound to fail.
The buskers claim their ability to make a reasonable living from entertaining Tube commuters has suffered a severe set back in recent times.
Undergound pitches at stations such as Green Park, Piccadilly and Bond Street used to yield up to pounds 300 a week.
Good acoustics and a large passing trade make the choicest Tube locations - positioned at the bottom of an escalator, for example - far more lucrative than pitches above ground.
But six months ago, London Underground and British Transport police introduced a tougher policy, partly in response to the growing phenomenon of train-hopping - where buskers go from carriage to carriage.
Police started to issue summonses rather than just moving buskers on.
Tex Lloyd, co-founder of the collective, said many established buskers who disapproved of train-hopping were being penalised for the actions of a minority.
Police were treating buskers 'like criminals,' he said. 'I've been busking for 12 years. I've had 15 summonses so far this year, that's more than in the past 10 years.'
Buskers and their legal representives have held meetings with transport bosses and British Transport police to discuss whether some form of licensing scheme can be introduced.
Above ground, in areas such as Covent Garden, licences are granted by local authorities, with conditions such as noise control. Organisers of the Covent Garden pitches audition acts and issue cards authorising them to perform.
Sessions are for 30 minutes half-hour and there is no fee to the buskers on the basis that they attract tourists to Covent Garden.
Angus Richardson, a solicitor acting for the buskers, said similar licensing below ground could be used to stipulate noise levels and gain some revenue for London Underground.
He said hiring a pitch could work 'in the same way as a kiosk on London Underground would work with franchising'.
There are only a number of limited pitches worth having. He also said that the purge on busking was wasting police time and resources.
He claimed that, in some cases, summonses which are made under Section 67 of the Transport Act 1962, which prevents performances and the soliciting of 'alms', were badly drawn up and being thrown out of court due to lack of evidence.
Inspector Kevin Colgan, of British Transport Police, who patrols the Underground, thinks licences would be a for disaster.
'You'd have to enforce licences which would exacerbate the problem with unlicensed buskers.'
London Underground said it could not endorse busking because of 'stringent safety conditions' which might require costly alterations to layouts.
FRANCO: I'M PROUD I MAKE PEOPLE HAPPY
Franco's working day starts at 7pm and finishes at midnight. His favourite pitch is at the bottom of an escalator at Piccadilly Circus Tube station. Franco is a trained musician who can play the accordion as skilfully as the saxophone or the drums. He said he was proud of his gift and is glad to share it, 'even if I play music in the 'wrong' places, I make people happy'.
Franco, 43, lives in Chalk Farm, and has been busking since 1985. Until 1983 he owned a shop in Carnaby Street selling badges and knick-knacks. Then a car crash stopped him working for two years and he lost his business.
His repertoire includes an accordion version of If I were a Rich Man but also extends to some Jimi Hendrix numbers and original compositions.
'When I started there was a game you needed to play,' he said. The transport police would come by. I'd say 'just moving boss', I'd leave and they would let me. No worries.' But over the past six months, Franco has accumulated plenty of problems: pounds 400-worth of fines and numerous summonses.
He said: 'This year they started booking, booking, booking. I don't understand. I was told I'm a safety hazard. I've saved several people from falling down the escalators.'
Whether he gets a licence or not, Franco says he is determined to carry on busking. Either solo or with his three-piece band. But, he admits, his life would be an awful lot easier if he could go legal.