UK rail unions have warned they may ballot more than 7,500 London Underground (LU) staff on plans for widespread strike action on the Tube network.
The National Union of Rail, Maritime and Transport Workers (RMT) and the Transport Salaried Staff Association (TSSA) have told LU the strike plans are due to an "unacceptable attack on safety standards".
The RMT is angry over ticket office closures, de-staffing, lone working and the use of agency and security staff, which it says compromises safety standards.
"When LU imposed driver-only tube trains it assured the public and its own drivers that good station staffing levels would keep the system safe, but those assurances are now being undermined," says RMT leader Bob Crow.
"The systematic denial of driving jobs and promotion to experienced Tube workers in favour of external recruitment is another serious problem that is undermining the safety culture."
The RMT and TSSA also claim LU plans to use sub-contractors to staff the Tube station at Heathrow's Terminal 5, due to open in March.
The unions say they will await a response from LU before announcing dates for strike action.
Transport for London was unavailable for comment but told the BBC the unions' ballot warning was "completely unreasonable".
By Ozge Ibrahim
