"Mixed-fleet" cabin crew, who are paid less than longer standing staff, will walk out for 14 days on 19 July, in a strike called by the Unite union.

The strike will begin three days after the end of the current 16-day strike.

BA said instead of striking, Unite should allow its members to vote on the pay deal reached two months ago.

The union said its members were continuing to campaign for a better pay deal.

"Today's announcement of a further escalation, underlines the determination of our members in their fight for better pay and against British Airways' bullying behaviour," said Unite's national officer, Oliver Richardson.

In its statement BA said: "It seems extraordinary that a trade union should ask its members to give up their pay and benefits for virtually the whole of July, trying to target the holidays of hard-working families, rather than give those members a chance to settle the central issue of the dispute."

'Normal schedule'

During the present strike, BA is leasing some Qatar Airways planes and crew to help minimise flight cancellations and passenger disruption.

BA said it was operating 99.5% of its normal schedule and that during the strike due to take place from 19 July it would "ensure all our customers reach their destinations".

Unite said: "The time and money British Airways is spending on wet leasing aircraft and bullying striking cabin crew are resources which could easily settle this dispute.

"It's high time British Airways stopped spending millions defending low pay and its bullying approach by negotiating a settlement to this long running dispute."

BA created the mixed fleet of cabin staff in the wake of a bitter dispute over pay and conditions for all cabin staff that ran from 2009 to 2011.

They fly only out of Heathrow, and on both short-haul and long-haul routes, but not in the same planes as colleagues on the legacy conditions of employment.

Unite estimates that, on average, mixed-fleet cabin crew earn £16,000 a year, including allowances.

BA has disputed these figures and says that annual pay is above £21,000 a year.