Ground staff at British airport operator BAA have voted to strike in a dispute over pay, the union Unite said, a move which could shut many of the country's busiest airports.
Unite said on Thursday its members at BAA, owned by Spanish group Ferrovial, had voted three-to-one in favour of industrial action.
The union called on the company to reopen negotiations on its pay dispute. BAA said the union had only gained weak backing for a strike after just half its members took part in the vote.
Unite said its officials would meet on August 16 to decide dates for any walk outs but added it was hoping to reach a settlement with BAA without having to resort to strikes. It will have to give seven days notice of any action.
"For the past four months BAA has refused to even meet with us," said Unite official Brendan Gold.
"BAA is doing passengers a great disservice by allowing this dispute to get to this stage. We are therefore calling on BAA to return to the negotiating table with a fair offer."
BAA said the vote would add to uncertainty for passengers, already hit this year by strikes by airline flight attendants and weather-related disruption.
British Airways, BAA's largest customer, remains in dispute with Unite over changes to cabin crew pay and conditions, which has resulted in 22 days of strikes so far, with no resolution in sight.
"We hope that the union will engage with us quickly to conclude an agreement," a BAA spokesman said.
"Fewer than half of those people eligible to vote have done so and we do not believe this result provides a clear mandate for strike action," he added.
Earlier on Thursday Prime Minister David Cameron criticised the strike threat, saying action would do "nothing but harm".
"These sorts of strikes never achieve anything apart from damage, damage to the business, damage to the jobs, damage to the interests of tourists who want to come to visit Britain or people who want to leave Britain and have a holiday," he said.
Unite balloted more than 6,000 BAA employees, including the security guards, firemen and engineers essential in keeping an airport running.
The union said 3,054 of those balloted had taken part in the vote, with 2,263 voting in favour and 791 against.
Regulations require minimum levels of staffing for airport fire stations and security gates, meaning BAA airports, which include London's Heathrow and Stansted, would likely be closed by strike action.
BAA's staff, who last year accepted a pay freeze, have been offered a 1 percent increase in earnings, plus an extra 0.5 percent conditional on changes to sickness agreements.
Unite, however, described the offer as "measly" and criticised the withdrawal of bonus payments, such as one conditional on BAA meeting its earnings targets -- which it missed by 3 percent.
In a separate ballot, BAA managerial, technical and support staff who are in dispute over the same pay offer, also voted in favour of strike action, the Prospect union said on Thursday.
BAA also operates Southampton, Glasgow, Aberdeen and Edinburgh airports.