Chief Treasury Secretary Danny Alexander said strike-related disruptions could damage the economy by $770 million if 2.6 million public sector employees carry through with a strike Wednesday over proposed pension changes, The Daily Telegraph reported.
Alexander said with many schools closed, parents would be forced to skip work and stay home.
Brendan Barber, the general secretary of the Trades Union Congress, dismissed Alexander's warning as fear-mongering and "fantasy economics," the newspaper said.
Meanwhile, the British Aviation Authority said a walk-out by the 4,000-strong Immigration Service Union would create 12-hour long delays at Heathrow International Airport and incoming passengers could be forced to remain in aircraft for hours.
That would create a logjam of parked aircraft and require rerouting flights to continental Europe, the authority said. The BAA has also advised airlines to restrict ticket sales to 50 percent capacity to expedite immigration screening by management and other non-union staff, the report said.