A Tube strike could be on the cards after Hammersmith and City line RMT drivers entered a dispute over what it calls an "overbearing management team".
The RMT union said that there had been a breakdown in industrial relations, and the National Executive Committee has advised that it is now in dispute.
The National Executive Committee said that it wants to arrange an immediate meeting with management.
The issue stems back to December, where a number of issues were raised, including breaches of the attendance at work policy, an overbearing management team, the refusal to release reps for meetings and the misuse of disciplinary policy.
However, the RMT says that some actions which were promised to address the issues haven't actually taken place, and industrial relations have deteriorated as a result.
The RMT added: "A further resolution has also been received from our Hammersmith and City branch calling for a ballot of train operator members at Edgware Road for strike action and action short of a strike due to a breakdown in industrial relations and abuse of agreements."