Members of Unite voted last year to take industrial action and were due to launch a 14-day walkout over Christmas before the airline took legal action to stop the strike.

The new ballot will close on February 22, raising the threat of action from March 1, although the union has ruled out any stoppages over Easter.

Unite warned that moves by the airline to recruit other staff to take the place of striking cabin crew members could put passengers' safety at risk.

The union said public concern will grow over plans to fast-track strike-breakers and highlighted the skills crew needed to care for passengers.

The union claimed a passenger on a BA long haul flight could have died last week were it not for the intervention, calm actions and dedicated care of the crew.

According to the union, one crew member on the flight told them: ''I'm about to collapse after a 16 and half hour day. We had one of the most serious medical incidents I have ever seen.

''A lady collapsed in the aisle, full plane. After 30 mins she fitted and died. We did CPR, defib (no shock advised) PA'd for a doctor - amazingly a heart surgeon came forward. Stabbed adrenaline into the heart.

''After around 20 mins he advised us to stop. 'She's dead,' he said. We replied that we have to continue for 30 mins.

''Four mins later we got a pulse. We supported her for an hour, breathing for her until she was passed to medics on the ground and is now in a hospital. As far as I know she is alive but very seriously ill.

''Imagine if strike-breakers were there today? I am sure we would have lost a fellow human being. These are the things we and the public should be worried about. It will cost lives.''

Len McCluskey, Unite's assistant general secretary, said: ''Cabin crew's dedication and skill kept a person alive when others had given up hope. BA should have nothing but praise for its loyal and dedicated cabin crew whose first and last instinct is to care for their passengers.

''Instead, BA resorts to intimidating them with macho threats to replace crew with vastly inexperienced volunteers. Not only does this show contempt for the crew, what message does it send to passengers who have paid to be cared for by a premier airline?

''Airlines are run by teams but this cynical ploy will destroy industrial relations at the company for years to come and trash this airline's brand along the way.''

Experienced crew have three months' training, but Unite said BA was planning a 21-day training programme for strike breakers.

Unite condemned BA's ''increasingly aggressive'' recruitment operation as an attempt to ''intimidate'' cabin crew out of taking industrial action.

Unite has warned the pilots' union Balpa that it was not acceptable for it to take a ''neutral'' stance over its members being used as possible strike-breakers.

Joint general secretary Tony Woodley said: ''It is not acceptable for trade unionists to act as strike-breakers in a legitimate industrial dispute, nor for pilots to use their privileged position to undermine much lower-paid trade union colleagues.

''Still less is it acceptable for their union, Balpa, to declare themselves neutral over strike-breaking. This is a clear breach of basic trade union principles, and I will be raising this matter urgently with the leadership of Balpa and with the TUC.''

Jim McAuslan, Balpa general secretary, said: ''Balpa and the vast majority of its members have a very different analysis of the situation in BA to representatives of the cabin crew union. We recognise the frustration that must have prompted so many cabin crew members to vote for strike action last year, but Balpa members were stunned by the threat of a 12 day strike at Christmas.

''Balpa is not in dispute with BA and if and when a strike is called by the cabin crew union we will issue guidance to our members to ensure they comply with the law and operate normally to fulfil their full range of duties.

''We understand a number of pilots have responded to BA's call for volunteers to keep the airline operating through any strike and from their postings it is clear that this is out of concern for their own futures and that of other employees. For the avoidance of doubt, Balpa's position on this is neutral and we will not dictate to our members.''