text: South Wimbledon and Queensway stations will be the first to see their staff moved from ticket offices into ticket halls and on to platforms.
  Transport for London (TfL) said it would save £50m annually as it tries to save £4.2bn by 2020.
  But Manuel Cortes, from the TSSA union, said London Mayor Boris Johnson was "rushing through" the closures.
  Mr Cortes, leader of the Transport Salaried Staffs Association said: "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 all stations would remain staffed and 150 new ticket machines would be installed by April 2016.
  It added that new visitor centres would be created at larger stations such as Victoria and King's Cross to help visitors.
  Nick Brown, London Underground's chief operating officer, said more staff were being placed "where they can offer the best possible assistance" as only 3% of Tube tickets were bought at ticket offices.
  He said: "This forms part of our wider vision for the Tube, which includes a 24-hour weekend service on core parts of the network."
  But the changes have led to previous strikes by the Aslef and RMT unions.
  Labour's London Assembly transport spokeswoman 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.
  "Whilst there is obviously a big role for ticket machines to play, there is no substitute for a member of staff."
  London Underground said after 100 meetings with unions the number of roles to be reduced had fallen from 950 to 897 with no member of staff facing compulsory redundancy or losing money.
target: Ticket offices will start closing on the London Underground later in a move that has prompted past strikes.