A new ballot of cabin crew at British Airways, for industrial action in their ongoing dispute with the airline, will be held next month.
The ballot will open on 1 March and close on 28 March, with the decision to be announced soon afterwards.
It will be the fourth ballot among BA cabin crew in the past two years.
The row began about cost cutting but now centres on travel concessions taken from striking staff and disciplinary action against Unite union members.
BA workers voted last month for further stoppages, but the Unite union said earlier this month it would hold a new vote after a "legal blitz" by the airline.
The airline had argued that the last ballot was unlawful.
Now Unite says that "systemic anti-union activity" at the company is preventing headway in negotiations.
It says that since 2010, 18 union members have been sacked and another 70 suspended, including a third of the local union leadership.
"If BA's management believes that it can secure industrial harmony by these methods, it is living in a fools' paradise," said Unite general secretary Len McCluskey.
"Only negotiation, not litigation or intimidation, can start to heal the wounds caused by this dispute."
He said the on-going failure of British Airways management to start negotiating, meant the need for a fresh ballot.
BA said "part from a tiny minority of hard-liners" everyone wanted the dispute to end.
"Should there be any further industrial action, we will implement our well-established contingency plans," a spokesman said.
They also said should a strike take place the airline would fly a full schedule at London City and London Gatwick, with 100% of Heathrow long-haul operations in place and many short-haul flights from the airport also in operation.
The dispute started in November 2009, when BA reduced the number of cabin crew on some long-haul flights from 15 to 14, and introduced a two-year pay freeze from 2010.
This led to a series of strikes in the spring and summer of last year.
Following these strikes, BA removed the travel concessions of those who took part, with some also facing disciplinary action.
It is this action by BA that is now central to the dispute, Unite says.
It wants the restoration of travel perks in full, arbitration through Acas of all cabin crew disciplinary cases related to the dispute, and restoration of pay to those who were genuinely sick during the dispute.
It also wants a full discussion about how BA has handled industrial relations within the company.