The High Court ruling yesterday did not uphold Unite's ballot of more than 12,000 cabin crew members, on strike action over pay and conditions at the airline.
Unite joint general secretaries Derek Simpson and Tony Woodley said: "While we have never wanted this dispute it is a disgraceful day for democracy when a court can overrule such an overwhelming decision by employees taken in a secret ballot.
"This dispute is not settled. Passing the buck to the courts to do management's job for them was never going to be the answer.
"British Airways must accept that there can be no resolution except through negotiation, failing which there will inevitably be a further ballot for industrial action.
"Given the clear mood of cabin crew about management's imposition of changes on their working lives, this means that the spectre of further disruption to the company's operations cannot be removed. Only a negotiated agreement can do that."
