Unions reacted angrily after British Airways asked its 40,000 staff to work without pay for up to a month in what Willie Walsh, the airline’s chief executive, dubbed the company’s “fight for survival”.

Mr Walsh's plea for staff to work free for between one and four weeks, which experts believe marks a first for a British public company, came in the week after he announced he would not draw a salary in July. That move will save BA £62,000, based on Mr Walsh’s basic annual salary of £743,000.

However, staff and unions pointed out that it is much easier to take a pay holiday when your salary is a significant multiple of many of your employees.

One BA cabin crew member told The Times: "We're all treating it like a joke. It's all very well for Willie Walsh, but my basic is only £11,000 a year."

“A lot of people are saying ‘if you pay off my mortgage, or pay my commuting costs, maybe we’ll consider it,” the crew member added.

A spokesman for Unite, the trade union, said: "Willie Walsh can afford to work for a month for free, but our members can't."

Mick Rix, national officer for aviation at the GMB union, added: “Until the BA executives accept permanent change to their remuneration and bonus awards then I would find it increasingly difficult to assume that most staff would take this request seriously.”

Mr Walsh’s request for his staff to take unpaid work comes hard on the heels of an earlier cost-saving initiative encouraging staff to voluntarily shift to a part-time position or take unpaid leave of between a month and a year. More than 1,000 staff have signed up to participate in those schemes since they were introduced last month, it emerged on Tuesday.

However, the call for unpaid work goes a step further than previous initiatives because BA is in a "fight for survival" said Mr Walsh, who announced last week that he would work for free in July, saving his airline £62,000. Keith Williams, BA’s chief financial officer, will also waive his salary next month.

BA made a £401 million loss in 2008, its biggest in 25 years, amid surging fuel costs and a collapse in premium-fare passenger. Total passenger numbers for the year to March 31 were down by 4.3 per cent to 33.1 million, as its fuel bill increased by 44.5 per cent to £3 billion on surging oil prices. Meanwhile, the number of premium-fare passengers - those travelling first or business class - declined by 17.7 per cent in April.

Mr Walsh has set a deadline of June 24 for employees to volunteer for unpaid work. He said that the salary deductions would be spread over three to six months wherever possible.

BA denied that those staff who volunteered for unpaid work would be given preference if the airline made compulsory job cuts. The airline has reduced its headcount by 2,500 since last summer, through voluntary redundancies and by not replacing staff who leave. It is currently negotiating pay deals and job reductions with its ground handling staff, pilots and cabin crew, who have been told that the airline needs to settle discussions by the end of the month. In total, BA is thought to be seeking as many as 4,000 additional job cuts, including 2,000 voluntary redundancies among the 14,000 cabin crew. This would bring the headcount reduction since last summer to about 6,500.

The request for volunteers to work for free was made in the company's BA news magazine. In an article titled Action Time, Mr Walsh wrote: "I am looking for every single part of the company to take part in some way. It really counts. We face a fight for survival. These are the toughest trading conditions we have ever seen and there simply are no green shoots."

"Our survival depends on everyone contributing to changes that permanently remove costs from every part of the business," he continued

Experts said that BA's request may set a precedent as companies continue to struggle to cut expenses.

Alex Lock, a partner at Beachcroft, a commercial law firm, said: "Many other companies will almost certainly follow suit if the take-up on unpaid work at BA is good. They will be watching it closely."

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