A plan to end a bitter, long-running dispute between British Airways and its cabin crew has collapsed.
The Unite union said the deal, drawn up at conciliation service Acas, would not be put to a ballot of its members.
The proposal had been called the best that could be achieved through negotiation.
But leaders of Unite union's Bassa branch - which represents most crew - would not endorse the deal, describing it as "a step too far".
BA said the deal on offer was "fair and reasonable".
The company said: "The way forward is for all sections of Unite to put aside their internal divisions and allow crew to have a direct say on their own future."
The proposal had been agreed after months of talks between the joint head of Unite, Tony Woodley, and the BA chief Willie Walsh.
But after Bassa's rejection, Mr Woodley said : "I will not under any circumstances recommend to our cabin crew members any offer that was not also recommended by our elected representatives."
He added "any sense that this offer is being presented to cabin crew over the heads of unwilling representatives would be deeply damaging to the union."
Mr Woodley said that BA had made it a precondition of the new offer that it was endorsed by the union.
Among the stumbling blocks, Bassa said, was a demand that the union gives up all outstanding legal claims arising from the dispute, and an acknowledgement that BA has the right to withdraw travel concessions from staff in future.
The airline's cabin crew workers have staged 22 days of strike action since March, costing the airline £150m.
When the dispute began in November last year, it centred on changes to staffing levels, pay and working conditions.
However, Unite has since said that the core issues are the removal of the travel concessions and the implementation of disciplinary sanctions against its members since March.
BA reported earlier this month that its passenger numbers in September were 1.3% higher than a year earlier.
However, its total traffic for the year to date is still down on a year ago, following the strike action and April's volcanic ash cloud which grounded flights across Europe.