Several ticket offices in Tube stations will start closing this month under a controversial programme to switch staff to platforms and make savings of £50 million a year.
Transport for London (TfL) said under a phased programme, staff will move from London Underground ticket offices to halls, gate lines and platforms.
Unions and Labour continued to attack the closures, warning that services to passengers will suffer.
TfL maintains that only 3% of Tube tickets are bought at ticket offices, saying there will be more LU staff on platforms than before and more available than ever to help customers buy the right ticket and plan journeys. Words: PA
More than 250 ticket offices will eventually close, with the loss of hundreds of jobs, although TfL said no compulsory redundancies were being made.
Nick Brown, London Underground's chief operating officer, said: "People - our customers and our staff - are at the centre of our approach to customer service. Throughout this year, passengers will see further improvements at stations, including more staff in ticket halls, on gate lines and platforms, where they can offer the best possible assistance. Our new customer service training programme is also under way, and staff are being equipped with the latest technology to help customers with their journeys.
Manuel Cortes, leader of the Transport Salaried Staffs Association accused London Mayor Boris Johnson of "rushing through" the closures, adding: "This is his biggest and most expensive vanity project to date. It will cost well over £150 million in the first year and that is not taking into account the fact that the night Tube will not break even until 2033.
"Talks on the safety implications of closing over 250 stations have not even been concluded. The Mayor doesn't seem concerned about how millions of tourists will cope with fewer staff to help them on their way."
TfL said 150 new ticket machines will be installed on the underground as well as new visitor centres at larger stations such as Victoria, Euston and King's Cross.
Labour's London Assembly transport spokesperson Val Shawcross said: "When he was elected Boris Johnson promised Londoners he would protect the capital's ticket offices, but today he starts the process of dismantling each and every one of them. Not only that, he is now intent on axing almost 900 Tube station staff in the process.
"Whilst there is obviously a big role for ticket machines to play, there is no substitute for a member of staff, particularly when you have a query more complex than a ticket purchase. The Mayor will no doubt find that passengers really do mind the gap left by his cuts to station staff and ticket office closures."
Mick Cash, leader of the Rail, Maritime and Transport union, said: "Today is the day when Mayor Boris Johnson not only rips up his promise to Londoners to retain ticket offices but also rips up the safety rule book and kicks off a closure and de-staffing programme that will turn the Tube into a criminals' paradise.
"The recent stabbing at Lancaster Gate of a member of staff has shown once again the vulnerability of both our members and the travelling public when numbers are sacrificed in the drive for cuts.
"RMT will continue to work with the community to stop a programme that takes out 1,000 jobs and every single ticket office and all industrial and political options remain at our disposal."
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