Tube drivers have voted to go on strike over the sacking of a colleague who it's claimed failed a breath test.
Members of the Rail, Maritime and Transport union have voted 229 votes to 221, to go on strike.
The Tube driver is said to have failed two random breath tests and lost their job as a result.
General secretary Mick Cash said: "Our members have voted for industrial action and the union will now consult extensively with our representatives before deciding on our next moves in this dispute.”
In defence of the driver, the RMT Unions has said the current system does not offer safeguards to those with disabilities or who are on certain diets.
RMT regional organiser John Leach rejected a number of allegations by LU operations director Mr Holness sent out in a letter to union members.
He said: "One of London Underground’s own doctors conceded that type 2 diabetes, liver disease and even fasting can give false positives on hand held machines. Underground bosses say they have a zero tolerance approach to alcohol and drugs.
Nigel Holness of London Underground said: "You wouldn't let someone who had been drinking alcohol drive your family in a car, and we don't let people who have been drinking alcohol drive people's families in Tube trains."
"As we have made clear, strike threats will not alter our commitment to safety, nor will they make us consider reinstating a driver who failed two alcohol breath tests.
"This makes the process more robust and also complies with the Equalities Act in protecting members of staff with medical conditions."
The case in question with the driver has gone through the full disciplinary process. The issue of diabetes is said to have been explored by the transport authority, who found the type of test would not change the outcome of the results if the person had the disease.
This same case triggered a 24-hour strike on the Northern Line by RMT workers in December.
London Live's Alison Earle joined The Evening News to discuss the new strike plans.