The biggest union at British Airways (BA) is to ballot baggage handlers and check-in staff in a dispute over pay, heightening the threat of airport chaos later in the summer, it was announced yesterday.

The Transport and General Workers Union (TGWU) said more than 8,000 workers will vote over the next few weeks after talks failed to resolve the deadlock.

Members of the GMB union at BA are already being asked to support a campaign of industrial action.

The TGWU said talks at the conciliation service Acas had not made enough progress to break the deadlock, adding that any chance of success had been blocked by BA insisting on an inflation-only deal.

The ballot was announced after the airline wrote to thousands of workers warning that industrial action would seriously damage the company.

The unions have rejected a three-year pay offer worth 8.5 per cent, or 10.5 per cent if it does not count towards pensions.

Brendan Gold, national officer of the TGWU, said: "With BA board's instruction of inflation-only pay increases, the people who are delivering for BA on the ground are working flat-out, but standing still on pay.

"The BA board is looking for low-paid workers to sort out its problems. The directors, who have just accepted a pay award of twice the inflation rate, are in effect refusing to acknowledge that our members have saved the company over £860 million each year."

BA took issue with the claim that directors had been given a pay rise of twice the inflation rate.

Chief executive Rod Eddington, director of operations Mike Street and finance director John Rishton have all recently given up bonus payments worth over £350,000.

Basic earnings for baggage handlers were about £14,000 a year, while check-in and administration staff, many of whom were women, earned £2,000 to £3,000 less, said the TGWU.