Sir Richard Branson has angered Virgin Atlantic staff who are threatening to strike by telling them they should “consider working elsewhere”.

The entrepreneur, estimated to be worth £3.1 billion, told 4,800 cabin crew in a letter that he would not meet their pay demands. He said: “For some of you, more pay than Virgin Atlantic can afford may be critical to your life-style and if that is the case you should consider working elsewhere.”

Union members have voted to stage 48-hour strikes on January 9-10 and January 16-17.

Sir Richard said he had drawn a line in the sand in the dispute with staff belonging to the Unite union, which is embroiled in separate negotiations with BAA, the airports operator.

“To go further would result in unacceptable risks and would set a dangerous precedent to the company,” he wrote. “It would be irresponsible of our management and they, rightly, are not going to take that risk.”

A spokesman for Unite said the letter was “insulting” and would worsen relations with employees.

The carrier has offered 8.3 per cent on basic pay over two years, with a 4.8 per cent increase in the first year. Sir Richard argued that staff using British Airways wages as a benchmark were being unrealistic. “It’s like comparing chalk with cheese,” he wrote, adding that Virgin Atlantic did not have the benefit of a history of state support and priority landing slots.

Paul Charles, Virgin Atlantic’s director of communications, said: “We have been inundated with calls from staff saying ‘we want to come into work to keep the airline flying’.”

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