British Airways says the proposed pay deal is "reasonable"

The Transport and General Workers Union took the decision after talks involving conciliation service Acas failed to resolve a long-running pay dispute.

The GMB union announced last week its members were to vote on strike action.

BA has written to 12,000 of its employees warning strike action over pay would seriously damage the company.

The TGWU said talks had been "stymied" by BA insisting on a pay offer worth 8.5% over three years, or 10.5% if the money did not count towards pensions.

But BA said it was extremely disappointed and did not want customers to suffer a "summer of misery".

We will keep talking BA spokesman

"We are hopeful of settling this without any stoppages and we are working hard to reach an agreement.

"We will keep talking, which is why we will continue with the ongoing talks at Acas in a bid to find a sensible resolution, which recognises the financial constraints under which we are operating."

About 4,500 baggage handlers at Heathrow, Gatwick, Birmingham, Manchester and Edinburgh and 3,700 check-in workers at the same airports, plus Glasgow, will vote between 5 and 18 August.

TGWU national officer Brendan Gold said the "inflation-only" rise would mean "people who are delivering for BA on the ground are working flat-out but standing still on pay".

"Our members are working harder than ever.

This is an immensely frustrating time TGWU national officer Brendan Gold

"With long-haul and short-haul flights flying at almost full capacity, they are at the sharp end of BA's increasingly robust recovery.

"This is an immensely frustrating time as they have worked extremely hard to exceed cost-cutting targets and are now feeling they have been slapped in the face."

The company's directors had just accepted a pay award of twice the inflation rate and were "looking for low-paid workers to sort out its problems", Mr Gold added.

BA denied directors had had such a big rise.

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

In a personal letter to staff on Wednesday, Mr Street said industrial action would cause "significant and serious damage" to BA's finances and reputation for customer service.

Unofficial walkout

The TGWU said basic earnings for baggage handlers were about �14,000 a year, while check-in and administration staff, many of whom were women, earned between �2,000 and �3,000 less.

And the union was asking for a "modest" rise in line with inflation plus lump sum payments, which would cost BA �50m over three years.

Last week the GMB described the workers as "the people who keep BA flying", and said there was money "sloshing around at BA for the board, managers and pilots".

There was serious disruption at Heathrow Airport last summer when check-in workers staged an unofficial walkout.

That dispute concerned a row over working conditions, including the use of swipe cards to clock in and out of work.