Campaigners have called for Transport for London to break the 'stranglehold' militant union hold over the capital by opening Tube driver jobs to external candidates.
The lucrative roles - which pay £72,000 a year - are almost never advertised to ordinary Londoners due to an agreement stuck with union barons, who fear allowing in outsiders could weaken 'workforce solidarity'.
The cosy deal attracted renewed anger today as London remains in the midst of yet another wave of industrial action that is set to cost the economy £250million.
A 24-hour strike by Rail, Maritime and Transport (RMT) drivers on Tuesday caused chaos for commuters across the capital again today, with another walkout set to follow on Thursday.
A TfL source insisted there was no ban on external recruitment, but the agreement with the unions requires any vacant positions to be advertised internally first. At this point, they are rapidly filled.
This contrasts by the approach taken by train companies, which regularly advertise for train drivers on public forums.
William Yarwood, campaigns director at the TaxPayers' Alliance, criticised the arrangement.
'It is an insult to Londoners that these closed shop roles remain a private members' club for union buddies,' he told the Daily Mail.
'By blocking external recruitment, unions kill off competition and artificially inflate wages, leaving taxpayers to bankroll a gold-plated payroll for a protected few.'
A shuttered Covent Garden Underground station this morning amid a walkout by Tube drivers
TfL insiders said that internal candidates bring 'useful system-specific knowledge' and suggested the policy of favouring existing staff was 'not unusual' across the British economy.
But Mr Yarwood called for the policy to be immediately reversed - even if that would inevitably mean yet another walkout by union members.
'TfL must break this stranglehold and open recruitment to the open market immediately to ensure the best value for commuters and taxpayers alike,' he said.
In 2013, the RMT lashed out against plans to open Tube driver jobs to non-TfL staff.
'We believe that the 'shortfall of successful applicants' is because of failings in the assessment and training process, which are rejecting capable candidates,' the union said, accusing Tube bosses of building a 'a pretext to recruit externally, to weaken the workforce solidarity that internal recruitment supports'.
Union leaders are resisting the introduction of a four-day working week, which they claim could raise fatigue and compromise safety. RMT boss Eddie Dempsey said: 'Transport for London (TfL) seems unwilling to make any concessions to avert strike action.'
But TfL has insisted the changes are voluntary, calling walkouts 'absolutely unnecessary'. Train drivers' union Aslef has accepted the changes, which would cut the average driver's working week from 36 to 35 hours.
An Aslef spokesperson said its union was 'surprised' that the RMT was going on strike, adding: 'It will be the first strike in the history of the trade union movement designed to stop people having a shorter working week and more time off'.
A Tube driver earns around £71,170 per year as a base salary, with total earnings often reaching £75,000 to £80,000 when overtime and allowances are included.
Commuters have taken to the roads on hire bikes in London today amid an ongoing strike by Tube drivers affiliated to the RMT union
Most are enrolled into the TfL pension fund, which requires drivers to pay in 5 per cent of their salary for an employer contributions of more than 33 per cent. Other perks include free TfL travel and 75 per cent off train season tickets.
How will the new Tube strikes impact you?
Tuesday and Thursday
The strikes run from 12pm Tuesday to 12pm Wednesday and 12pm Thursday to 12pm Friday.
Services will begin to recover from midday, but disruption will continue into the evening.
A reduced service will run across most lines but significant disruption is expected.
No service expected on the Piccadilly and Circle lines. No service expected on the Metropolitan line between Baker Street and Aldgate. No service expected on the Central line between White City and Liverpool Street.
Any services that do run will be less frequent, very busy, and passengers may not be able to board the first train.
Alternative options
During the strikes, other TfL services including Elizabeth line, DLR, London Overground, Trams and most bus routes are expected to be running normally, although they are likely to be very busy. On Friday, a bus strike will impact a few routes in east London.
Tube drivers do not require prior qualifications other than GCSEs in maths and English and training takes around six months.
On most Underground lines, the trains are semi-autonomous. This means a machine handles stopping and starting, with drivers operating doors and handling emergencies.
Simon French, chief economist at independent investment bank Panmure Liberum, has estimated the cost of the strikes as £210million.
The strikes have forced the hands of City firms that usually demand workers come into the office, with some telling workers they can work from home.
And commuters deprived of their usual Tube line have taken to the roads in droves as they try to find other means of getting to work.
Susan Hall, leader of the Conservatives' City Hall group, told the Mail: 'This is going to damage the tourist trade even more, while Sadiq Khan sits in his chauffeur-driven car.
'He doesn't understand how it is for the people trying to get to work, earning a lot less than these Tube drivers.
'The unions are so used to striking they will find any reason to do so, it appears, knowing this Government will give them anything they want.
'There is no way Labour is on the side of working people, otherwise it would be doing what it can to make sure they can get to work.'
The RMT has been contacted for comment.