The UK's biggest rail union has accused Transport for London (TfL) of "lying" over staffing levels on the Tube.
The Rail Maritime and Transport (RMT) union said a leaked document showed some stations were being left unmanned.
TfL claimed no stations would be unmanned, the RMT said. But the report says "stations across the network are left unstaffed from time to time".
TfL admitted the document existed but denied lying and said stations would only be unmanned on "rare occasions".
RMT general secretary Bob Crow said: "The management claim that they have no plans for unstaffed stations as a result of the cuts is a total lie.
"Once again TfL have been caught out lying about the service and safety impact of their station staff jobs cuts plans.
"They have repeatedly told the public that they have no plans to run unstaffed stations and yet this communications report shows that that is exactly what they are planning for."
A TfL spokeswoman said: "London Underground has staff at all stations and staff rostered for shifts covering all hours that a station operates. This will not change.
"On rare occasions, at small above-ground stations, when staff are not available for short periods due to sickness or other unplanned circumstances, a station maybe left unstaffed temporarily while another member of staff is found.
"This is preferable to closing the station and causing inconvenience to passengers."
Members of both unions have staged three 24-hour strikes in recent weeks over plans to cut ticket office jobs.
A fourth strike is planned for 29 November. Union leaders have said they have no plans to disrupt services over Christmas and the new year.
Talks at the conciliation service Acas aimed at resolving the dispute were adjourned were taking place on Thursday.